Stuck To The Plan:
In this world Pompey refuses to listen to the Senators pestering him to end the war with Julius Caesar quickly and keeps to his original plan of waiting Caesar out. When he does go to battle nearly a month later he commands an army several times larger than Caesar's and also several times fresher. Caesar's army whilst battle-hardened and loyal is also starved and weary. The battle ends in Pompey's victory and Caesar is killed. His supporters would survive here and there for several more years before they are hunted down. The Senate return to Rome to rebuild their power base and finish off Caesar's followers, Pompey is commended, returns to retirement and is then promptly assassinated shortly after the war ends.
However the Roman Republic had only bought itself a little respite. Politically minded generals still went out to conquer new lands and gain popularity with the army and the people all while the corruption in the Senate continued to fester and grow. Eventually an monarchy was established around 144 AD. Funnily enough it incorporated some features of the old Republic transforming into an elected monarchy. Candidates for the position of Imperator were all from prominent families but unlike the Senate the person sitting on the throne did have most of the central authority and power. Like OTL the Roman empire's power would wax and wane. Under a particularly talented dynasty (who managed to get win three consecutive elections to the throne) they actually reached even greater heights than the Empire under Trajan. Of course size, corruption, overstretch and internal divisions began to cripple the empire from the inside whilst wars with Parthia (later Persia) and barbarian invasions served to destroy them from the outside.
In Judea a religion was formed combining certain aspects Greek and Egyptian religion around a solid core of Judaism to create a Christianity analogue. It would later absorb aspects of Zoroastrianism as well and become rather popular in West Asia and Egypt. However it struggled to make it into Europe and mostly stuck to the Balkans and Italy, it would become more popular in east and North Africa as traders spread it south and west from Egypt. In Europe itself the Romans would gravitate more towards gods such as Sol Invictus, Mithras and funnily enough, Isis as central religious figures with a bit of emperor-worship thrown in.
The Roman Empire's collapse was much like OTL's but the migration patterns of the various tribes and cultures coming into the Empire were different. Rome's legacy would survive strongest in the South, around the Mediterranean whilst their Northern territories would be absorbed by barbarian cultures. Rome's legacy in the North would continue in the form of the various new religions derived from their more popular cults and in their language. Most literate people in Northern Europe would be scholars who were taught Latin, this in turn having an affect on most of the ruling classes as literacy was reintroduced to the North. In the proceeding centuries numerous successor kingdoms would emerge, all claiming the title of Emperor of the Romans. Genuine rump states would survive in Anatolia and Egypt but they were evangelised by this point and mostly Greek to begin with.
The post-Roman status quo would be shaken up once again around the 9th Century with the Arabic expansion. Islam would never develop but the Arabs would still reach a critical mass and move out to acquire new and richer territory. Following them would be a virulent form of Christianity that would rise to dominance in Persia, Mesopotamia, the Caucasus and other portions of West Asia. The Arabic empire would collapse a century later, reaching its peak around 821 Ascensio Thronem Romani (965 AD), leaving few successor states. Their greatest legacy would be the spread of Christianity further into Asia and down East Africa. Over the Middle Ages there would be a sort of religious struggle between Tengriism and various Christian/Judaism denominations. Christianity would also become dominant in Northern Africa. Without Islam in India Buddhism would remain fairly strong in parts of the subcontinent and evolve as it interacted further with Hinduism.
There have been several Roman Empires, mostly in Europe and they have all risen and fallen, waxed and waned. However the most recent owner of the title is actually based in the Hesperides (this Tls Americas). The Roman Empire of Hesperia is a Latin/Amerindian state with a mostly creole population. They speak Latin with a number of loan words from the more numerous and homogeneous indigenous cultures. Most of the remaining pure Amerindian societies in the Empire do maintain their traditional languages though. Hesperia is a sort of bureaucratic monarchy that maintains the traditional absolute monarchy on paper but gives all of the power to the bureaucrats, appointed ministers and various other government professionals. The emperor is not elected anymore and has been ruled over by the same dynasty for a couple of centuries now. The royal family have been enthusiastic sponsors of industrialisation and technological progress but they have fallen behind most other powers in terms of modern high technology. Their resource base gave them a strong platform for modernisation and they are a top tier great power.
Hesperia's dependencies are a mixed bag of settled European ex-colonies, Amerindian states and a variety of semi-assimilated and creole nations. Most are essentially colonies but there are exceptions here and there that are all still subservient to the government in Nova Capua.
The Mediterranean was where Roman civilization rallied and it is here that several different nations claim their legacy. The New Roman Republic is unfortunately very pathetic and has little about it that is noteworthy other than control of Rome itself. Fear of retaliation from the other powers is what keeps larger nations from attacking them. Hispania used to be a great power and founded numerous colonies in the Hesperides. Whilst their original colonies were long ago absorbed by Hesperia they have built a small empire in Africa. By far the strongest is the Aegyptian Empire. Despite a short Arabic rule in the Middle Ages the Greek/indigenous cultural and linguistic core survived and quickly overthrew the Arabs, returning to their old form of governance. They are Christian and have worked hard to evangelise their new territories in Africa. Whilst they did fall behind most other great European powers they have bounced back. After decades of resistance their colonies are being granted full independence. First the Emperor's government is making sure that their economies are completely under Alexandria's control before they remove all forms of old colonial government.
The British Isles have been the melting pot of Europe with incursions from Germanic and Nordic peoples as well as frequent conquest from Latin/Roman successor states based in Gaul during the Middle Ages. Britain would go on to build a large empire and successfully industrialise, capitalising on its wealth of natural resources in order to do so. Then in 1762 ATR (1906 AD) revolution broke out in the overcrowded and poverty stricken cities of the north. The revolution engulfed the island and the government was forced to flee. They set up a government in exile in their developed colonies in the Hesperides, evacuating the monarchy and most of the aristocracy as they did so. The Britannian Empire has decentralised by necessity into various different viceroyalties, each with a branch of the royal family on the throne. They follow the Roman and Nordic tradition of electing their emperor from amongst the viceroys of the empire. The current emperor was chosen from one of the African viceroys and has used this as an opportunity to sponsor further development and expansion of infrastructure on the continent. Whilst the Britannians no longer keep slaves the blacks of African and the descendants of slaves in the Hesperides can expect poor treatment and the worst jobs in the Empire. Thankfully things are improving and the remaining indigenous elites are rising to power. They may not be overly concerned with the plight of their poorer brethren but a powerful upper and middle class is growing. Britannia is probably the most backward of the great powers with much of their empire still undeveloped but they are making steady progress.
The white population receive the most privileges as full citizens of the empire. Whilst there are differences in accent, dialect and a few differences in slang the Britannians for the most part speak a Germanic language with a lot of influences from Latin (more so than OTL English). The non-white population often speak their own indigenous languages but are expected to learn Britannian in order to interact with the white population. This has actually served to keep the non-white population divided and prevent nationalist ideals from properly forming. Britannia is fairly hierarchical and hold a lot of significance to social cohesion and order. The aristocracy are respected and hold genuine power but there is an element of Darwinian meritocracy in their thinking that often allows for some class mobility if a person is cunning and talented enough to do so. Even some non-whites have been able to climb up the ladder.
The European world is finally being challenged by new powers. The states of China used to be constantly warring and were often exploited or conquered by European and Hesperidean powers. However an enterprising and intelligent warlord finally managed to reunite most of the Chinese kingdoms in the early 18th Century (20th Century OTL). This new Chinese Empire has been industrialising ever since and is now a massive and belligerent power. Authoritarian and xenophobic they intend to oust all European influences from East Asia and build a new empire/alliance system to challenge European power elsewhere. No-one in the neighbourhood's biting yet though Their main opponent in this endeavour is the Empire of Yamatai who are an efficient state with an elected monarchy, a surprisingly industrious population and a culturally ingrained grudge against the people of the Chinese mainland. They also were able to beat the Chinese and the Turks to the punch when colonising Manchuria and several other areas. What they did to the Koreans during their expansionist phase was regrettable but they have tried to make it up to them in recent years. They are currently being supported by both the Hesperians and the Britannians in order to curtail Chinese expansion. The Persians and the Turks are not that worrying for the great powers but they are still worth keeping an eye on lest they surprise the rest of the world.
Technologically this worlds is at about the same level as OTL. A higher degree of industrialisation and a greater degree of investment in colonial territories has been offset by the more authoritarian nature of this world. In many nations technological advancement was given an engineers perspective rather than a scientists. What already existed would be improved in order to make it more efficient in place of seeking completely new innovations. Today this attitude has largely been abandoned now that high technology has become so important. There is an internet of sorts and it does cross national boundaries but it is still not as extensive as OTL' and it is prone to censorship. This world is more prone to political paranoia and belligerence which has been used to justify the extension of state surveillance in most nations. Every major country has a secret police that monitor the population for the purposes of state security. It so not uncommon for people to go missing for the purposes of interrogation. However a form of human rights does exist that keeps these state forces from subjecting the people they detain to inhuman abuse and torture. Slavery was abolished at the end of the 18th Century (19th Century OTL) largely for economic reasons. Due to the survival of more Asian empires and the puppetization of West Africa there has been less scientific racism. Africans have still received the worst of it but Asian cultures at the very least have been spared.
Whilst most nations are authoritarian there is still genuine democracy. Elected monarchies are actually more common than hereditary ones in Europe and constitutions of various forms are upheld in most great powers. A form of socialism still developed but outside of the British Isles and a few other backwaters it has yet to actually take hold of anything of substance. Imperialism is still going fairly strong but it has transforming into a new system over the past few decades. The cost of subjugating regions has outgrown the benefits but the idea of assimilating colonial territories and investing in them is proving to be more popular. Nuclear weaponry is a bit of a problem as the Cold War of this world has in fact been a multi-polar conflict with more power blocs based around individual empires. The nuclear Sword of Damocles still hangs over everyone’s heads and world leaders all tread carefully in order to make sure they are not the ones who cause it to fall on them.