I think your consideration isn't bad and many, including myself, believe China won't attack...unless there's a weak US President/leadership. Consider that Crimea was invaded under Obama but Ukraine was outside the west's protection; same can currently be said of Taiwan but Taiwan is less about what is has to offer to the west (beyond a western friendship) and more about containing China deep into their waters. Ukraine had a lot of political tensions in the early 2010s and I think Obama was stuck in a nuanced position that ultimately boiled down to: how committed and effective will Ukraine be against Russia (corruption was a huge consideration around 2014). But Obama should have done more (including the EU) sooner. This allowed Trump to play both sides: publicly lick Putin's boots while allowing military assistance to Ukraine - pleasing the military complex at the very least, regardless of who won. But even as Trump's administration was wrapping up their mess, you could tell some in the GOP were setting a stage for pulling back military assistance; still are trying. Biden made sure assistance was unwavering and wants to degrade Russia in the eyes of the world while the west's military complex shovels in taxpayer money. Taiwan, under Democrat leadership, is an easy choice: they're not corrupt even with their wing of China friendly politicians, they're trained and continue to be armed to the teeth with only one purpose: hold until the west comes to their defense (including S Korea and Japan). I honestly believe Hong Kong was too hard to defend from China but perhaps it might have played out differently under a Democrat POTUS. Lastly, Taiwan doesn't have to "win" so much as make sure China doesn't win; I think the US would be fine with another North South Korea tension if it keep China in their waters and off of Taiwan and their waters; most notably off of their eastern waters/shores.

I'd be surprised if any country responded militarily. It's not in the interest of anyone to risk WW3 over Taiwan, and China knows this. In contrast to Russia, they are probably competent enough to take Taiwan in a day or two before anyone can send significant aid.

There would be massive economic implications though. The most effective deterrence that western countries have are sanctions, and they can't let China invade without consequences to keep the deterrence effective (also for other countries), so they'd have to be used. Investment in China would probably be banned for decades to reduce reliance.

If hundreds of millions of Chinese fall back into poverty due to the invasion, that would be a serious threat for political stability in China.