The second American Civil War.
The North vs South.
The United States agreed to enter into a World Peace Pact that would eliminate the need for world boundaries, unique currency, and military force. The Southern States weren't into that idea, convinced of its inevitable failure. A war was fought - but the south lost.
The Killer Dead takes place after the events of the second American Civil War. As far as your character knows, the end of the war brought about such destruction that the south seems to be in a post apocalyptic state. For one reason or another they find themselves in Dallas, Texas, and things aren't quite how they remember it. Phones are down. Internet. Any form of communication seems non existent save for an occasional radio broadcast. But worst of all - the dead are walking. There are signs everywhere though - a safe haven exists in Austin.
You gotta get there.
Unbeknownst to our contestants (for now), all their actions are being recorded. Live. Broadcast with the help of Nippon Network, Japan, in true high stakes reality show style..