As far as I can tell, the Chinese have no concept of quality. Their equipment would be very prone to breaking down. I would suggest that even in total war, the Chinese would be quick to lose. Their missiles and "advanced" technology would break down. The only reason they can even produce quality iPhones is because Americans work there for QA.
The US would be crushingly superior in the sea and air, in the event of a war. Camacho already put it better than me, so I don't need to go into the details. It's these guerrilla wars that are the fatal weakness of the Yank military, because their strength is their massive conventional firepower, and they often don't know exactly how to respond to terrorism or insurgencies, so they usually botch it (see: Vietnam). However, if it came to a conventional shooting war against another superpower, the Yanks would be in their perfect natural element.
The PLA might outnumber them on the ground, but that doesn't matter much, since the US has devastating air power. No way could the Chinese match the Yanks in the air - their material is so fucking shoddy, half the Chinese planes wouldn't even take off the ground.