Short term, we would have a lot to lose in going to war with China. Besides the umpteen millions in casualties, we'd be losing a quiet ally in the war on terror.
China shares a border with some very Islamic nations, and has nothing to gain by seeing fundamentalist Islam forces gaining power anywhere in Asia or the Middle East. Notice how quiet China was with all the American military presence in Afghanistan and Kzyrgistan (sp?)? China doesn't want to see fundamentalist Islam spread any more than the U.S. does.
Also, for you Clancy fans, check out The Bear and the Dragon (or something like that). It's China attacking Russia, and Russia joining NATO (sound familiar?). Russia has a lot of what China wants - raw materials in minerals and oil. It's my opinion that if the fur ever flew, Russia would be one of the good guys against China.