America could stop China only with WW3. Whether China will invade Japan or just will attack Japan by sea and wait to see what happens while the Koreans battle, I don't know. But it is illusion that several nukes of USA will fix it all. China is a nuclear power and recent estimates put its numbers well beyond 200, may be 2000 warheads. Everyone of the nuke powers builds up, only USA and Russia scrap nukes. The idea of a winnable WW3 with several preemptive nukes is absurd. WW3 if happens, will be massive and one sided - one of the sides should launch thousands nukes instantaneously and without warning to disable the other. If it is uSA, it should nuke both Russian and Chinese ICBM and submarines fast enough. Still some will survive and most likely retaliate. So there will be 100 US cities ruined as a result, even from only one sub. If that is a victory for USA, be my guest. The other scenario is much more terrible, i.e. Russia and China attack first when decided WW3 is unavoidable. Because they don't care of 100 cities ruined, so to speak. In other words, USA will lose WW3 even if it wins it. I don't know what the long term goals of Chinese might be, who might actually want to cut their population with 1/2 or even 2/3 in a 100 years perspective, so they might welcome a US strike that will leave them winners on Earth in long term perspective. Also we don't know what the India-Pakistan madness will produce. By now they should have hundreds of nukes if not more.