China has no interest in funding terrorist attacks against the U.S. or anyone else. They want to be a Great Power, not a rogue state.

Aside from nukes, which would draw an obvious and unstoppable reprisal from the U.S., China does not have the military capability to meaningfully threaten the U.S. They don't have the aircraft, ships, subs, landing craft, etc. And again, I don't know why they would want that.

They do have the means to threaten their regional neighbors, though, and some of them are U.S. allies. That's the WWIII threat: that Chinese regional aggression sucks the U.S. into a military confrontation on China's turf.

Interesting. I feel I could say the same of the USA vs China - any outright attack against China would draw a massive response, and I hardly believe the USA is capable of occupying China in any meaningful way.

Well, I'm not sure what you mean by "massive response" as China's nuclear capability is more for regional prurposes (i.e. India) though I do believe they have some ICBMs capable of reaching anywhere in north america. But their military resources are much smaller (e.g. they only have a couple of aircraft carriers and no supercarriers) and the PLA isn't really set up for projection of force at a distance.

I do agree to the extent that though the US would win any initial skirmish the long term viability of such an effort close to or on the Chinese mainland is probably not great.

Then again I can't come up with any reason the US would want to fight a war with China either (or vice versa), but who knows these days.