If Chinese territory was hit by US weapon on their industries, China will definitely hit back at US mainland and their industries.
With long range missile of course. With how many missiles? Even hundred of missiles like what Russian and Iran did to Ukraine and Israel could only do little damages. Maybe some buildings would be destroyed. But that's it. Unless both sides use nuclear.
But US can hit China from any where from Japan, Philippine and other countries around China, and China at the same time must bomb those countries into stone ages. So China will bombs those US allies more than they think about to strike US mainland. So the battlefield won't be in US mainland, but around China. It will devastate Japan, Philippine, Taiwan, and maybe Vietnam (if they foolishly join the war) but compared to China, US is basically intact. If that happen, US main objective is complete. Because anything that can disturb China economy and industry can be considered victory to them. Who care about Japan, Korea, and Philippine. They just sacrificial lambs to them.
So this come to my idea. US main weakness is their logistical route. I use the ancient Wei Qi logic for this. Remember, there are 3 steps of strategy in military warfare. From tactic, operation, to strategic level. My idea cover to strategic level only. If we portrayed China and US pivot in SCS and westpac situation, the area that east to Japan and Philippine is basically US "Territory". It is difficult for China do disturb US logistic ships that operate in Pacific Ocean. Specially when they are guarded by US Navy element. Because compared to US, China ability to reach Pacific Ocean is more or less limited. Even if they can, it is basically behind the enemy land. Their are at their own. There is too little support that China mainland can offer to support them.
To interrupt US plan to pivot China, They have to have an easy access to the Pacific ocean. Maybe from Eastern Russia mainland, or another countries that has access to the ocean without any US ally. Like Indonesia maybe, or Papua Nu Guinea. If China can build a Submarine base there, China already can limit the US "Liberty" (Wei Qi chess term) in Pacific. Thus decrease the effectiveness of their Asia pivot. As China can disturb their logistic route without any problem.
So this is the reason why US more afraid if China can get an ally in Pacific Ocean than anything else. Sometime ago I read that a small island country in the Pacific give China the access to their port. And you know, this already freak US and Australia out. Because it is basically very dangerous to their position in Pacific Ocean. So what if China can put their grip into that country, by building a military base there and protect the regime from any US and Australia attempt of "Arab Spring"? It will change the course of US' Asian pivot strategy. That's what I mean from my Wei Qi chess strategy in WestPac.