I’d say if they wanted “realistic” i’d go with China, but the last time an modern shooters tried to include China as the bad guy (COD Black Ops 2 and Battlefield 4) they weren’t too happy about it and i don’t think the US wants to piss off China.
Speaking of, I joined my first TF2 servers yesterday. One was a CTF server where I, as Scout, just kept running in and stealing the intelligence while everyone else was fighting at the bridge. Eventually it stalemated before I got boxed into spawn.
So basically all the conflict in the Ace Combat world of Strangereal can be traced back to a comet coming to give one continent a bad time, and one nation not wanting to lose their land so bad they nuke themselves 7 times.