No, America is not. Some think it is, by a very vague reference, but it’s of no significance.
But actually, they both can still be the number 1 and 2 economies in the world and still have no significance in the final war over there. They may very well be drawn in at the last minute, but they will have played no part leading up to it.
How can someone be drawn into something when they have been completely defeated? (EMP as asymmetrical warfare)
As for China, I have no idea how they don't end up in the final act...