Sorry, not even close. Given the backstory to the game, America showing up is far more plausible than China showing up which, like I said above, would be too much of a stretch.
Given the economics of game development and the game's region, it's probably safe to say the US Marines and British Army will be among the first NATO combatants added in a module. Poland is probably also a strong candidate. Germany....maybe. Their military isn't all that geared right now for a big-time military clash, and politically their population is very much against deploying the military for offensive operations. That, and to paraphrase one of the ISAF commanders, their performance in Afghanistan resembled an "aggressive camping trip."
There'd also be of course the whole psychological matter of sending the German military back to what was its graveyard in WWII.