This kind of thinking gave us the First World War.
If the US stops protecting Taiwan and allows China to take it by force, it can kiss their credibility worldwide goodbye, dismantling its entire network of allies built over decades in one fell swoop.
Not impossible, but world empires do not generally do such things unless they are very, very weakened.
Isnt Taiwan too valuable right now for the US specially TSMC. US will need to step in to protect Taiwan to protect US interests.
Look at where we are now :|
The point is that a war won by the US will destroy the winner too. Did you just downvote and comment without even reading the post or what?
Theoretically, yes. Practically, the last war formally declared by Congress was in June 1942 against Bulgaria, Hungary, Romania. Since then, all the military conflicts that the US took part in were driven by the executive.