I think the US vs. PRC is a stalemate on both sides. Pound for pound, our soldiers win, but they have the "extra" pounds to offset us. We could not "take and hold"any part of mainland china, because they would be frantic to "push us out" and we likely would have to either give ground or be overwhelmed. I don't see where China has the experience. Half a billion peasants with AK's is alot of AK's to overcome, even if they are untrained [unlikely] or ill trained and inexperienced [more likely].
OTOH, China likely could not "take and hold"any part of the US, in our case partially because of our armed populace. We wouldn't be able to bring the overwhelming numbers to bear that they could, but we wouldn't need to. We have millions of gun owners that I think would prove next to impossible to "pacify". We've all see Red Dawn, one to many times [is that possible?] and I think the vast majority of us would stand up to the threat, reguardless of any actions by our own army and .gov. Think there's alot of insurgents in Iraq? Try invading the US.
Logistics would likely be the Achillies heel of either attempt. Nukes would also be problematic except as the same type of use as in WW2, as a means to force capitulation, NOT as a way to destroy troops.
I used to believe that the IDF was, pound for pound, the toughest fighting force out there, but that was before the gulf wars where the US "caught up" in terms of real world experience. Lord knows how much of a difference, one talented, motivated NCO can make during the course of a battle, and now we have plenty of them.