banned for stating it if you're not going to go over.
Yes, I agree that neither side would go long without vaporizing the other, but it's a game where nukes would bring a quick end to the fun.
As for Europe, Asia, etc... Keep in mind a few conflicts and such...
Asia was largely brought together, but some could argue never totally. Not all of Southeast Asia actually fell, but largely because it was ignored. But yes, it was largely unified at one time. Of course, a common practice of older Eastern cultures was to allow invaders in and then assimilate them, thus it was no biggy.
The Middle East is not totally homogenous, geographically or culturally. Although Islam helped at one point to unify people, after Mohammad died, it quickly split and newcomers were seen as outsiders. Islam had a similar history to Alexander's Hellenistic Empire. And if you were to say an Arab was the same as a Persian, both would take offense, despite both being largely Islamic. It was really only in the times of Mohammad and Saladin that it was united, even if tenuously. Before Islam, though, cultural assimilation was a constant and so invaders were unwelcome, but often tolerated once everyone knew who bested who.
Europe was not exactly unified. The Roman Empire got the closest, but was unwilling to breach into Scandinavia and much of the northeastern area because the Germanic tribes were an absolute nightmare to contend with after a point. Containment was preferred over invasion, but they still did a very good job. Alexander had a bigger empire, but went the opposite direction. Charlemagne attempted to bring together Europe (as did Hitler and Napoleon) with the hopes of uniting all tribes of Germanic origin, but fell short in the same fashion as the Roman Empire (as did Hitler and Napoleon). I think one of the biggest conflicts with such an endeavor is the cultural dynamic of Europe. Europe had a huge influx of peoples with the same background, later known as Celts collectively. These people could spread out and didn't have too many issues. Then the migration exploded from the Caucus Mountains, sending only one group out toward India and a plethora of people toward Europe. So suddenly it's crowded with all sorts of ideologies. So people are going to start bashing heads in for space (and the poor Celts were not anticipating this). Because the cultural tendency was that of resistance and so many groups had to constantly vie for space, these people became hardened, a reason I believe Europe was destined to carve some impressive territories out of the rest of the world. Not saying they're better, just better at violence.