The US promise to defend Taiwan is premised on an unprovoked Chinese attack. This is when China will have the least geopolitical support from countries like Singapore or South Korea, who'll see China as disrupting the status quo for no good reason.
The US hasn't promised to create an independent Taiwan and would have much less support for that.
You have to remember how the enemy thinks. They believe every opponent is Hitler, who just wants to conquer the world in a series of unprovoked attacks. They believe China will act like Russia and launch a surprise attack. Rationally, China is much more likely to wait for the ROC side to act first and only react later. That's what they've always done so far. Nobody stopped Pelosi from visiting, but there was a strong response to that.
The Ukraine war is actually helpful for China because it deligitimises referendum based declarations of independence or joining Russia. The Americans might ignore that, but at least Europeans would be much less happy to fight China if Taiwan is seen to have brought trouble on themselves.