Interesting point, it does kind of sound like the US and USSR interfering in the Middle East. I probably would believe you, save the fact that Ace Combat always portrays it as "American" (At least in the American version). Everyone speaks plain English, (I think) the voice actors are all white, the weapons are all quite modern, the economy is modern, etc. I've always wondered if Osea went crazy with colonization, and colonized (And maybe exterminated the local population) Usea, Gracemeria, and maybe Aurelia.

No the reason for the American voice is simply for gameplay. If u watch the cutscenes for yuktobania, they have Russian accents. Belkans sound American too. But in the cutscenes they have German accents. They do this all the time in video games. For example in call of duty ghosts, the federation is South American, yet he has an American accent. So yeah. Plus the möbius squadron is not even usean, they are mercenaries. They are probably osean.

Mobius Squadron is not comprised of mercenaries since ISAF would, otherwise, be like a regular armed service like that of individual countries. And Usea is, so far, the only place in Strangereal where English accents can be heard.