No, not perfect. We don't know who launched the first bombs. And we also don't know if China was also making products of their own. They made stealth armor that the U.S. couldn't replicate very well. I think China was suffering a bit more than the U.S. though.

Canadians have power armor? I thought they were all being executed by U.S soldiers....?

can i get a wiki link about pre-war USA

http://fallout.wikia.com/wiki/USA

I'm inclined to say the U.S.
But only because we don't really know anything about what happened to China. As someone said, they may have had it worse resource-wise, but the communist system likely did wonders for stability, whereas much of the problems in the U.S. were stability problems, with rebellions and whatnot.