Not really. The M4's receiver is pretty closed. The only real place for dirt ingress is the ejection port, which has a dust cover when not being fired and has gas knocking out potential sludge when being fired. There have been tests where AR15s and AKs are dunked in mud and the AR15 keeps going and the AK fouls after a single round.
Because the AKs receiver is very open, it's easy for dirt to get in. The AK's locking system isn't that different from any other dual-locking lug bolt head, so dust will foul it.
Over the long term, an AR15 would probably need more maintenance than an AK to stay reliable just because there is more precise machining there, but an AR15 will be more reliable in a harsh environment than an AK. Problems with reliability with the very first M16s issued in Vietnam weren't so much because of the platform, but because the government issued soldiers out of spec ammo which the gun wasn't design for, and they didn't issue cleaning kits. Guns need to be cleaned.