The US is ambiguous about Taiwan, but, they have sent signals that they would not support Taiwan should Taiwan declare independence. Hell, the US couldn’t do much about Ukraine.
The US is fine with independence. Its big concern is no “unilateral” decision by either China or Taiwan, and you will see that word repeated time and time again in Washington press releases. Basically they say this as a hedge against China suddenly invading. Any solution is an acceptable one as long as Taiwan and China are on board and there is little chance of conflict.
I, like US, also do not support “declaration” of Independence because even the act of supporting it would imply I concede Taiwan is a part of China.
Declaration is not really necessary in making a country sovereign. Canada never declared independence. Ironically I’ve seen more pro-China folks daring Taiwan to declare independence as if currently it were not already independent vis-a-vis China.
What I and US have no problem supporting is calling Taiwan exactly as “Taiwan” and phase out any ROC namesake.
Legally speaking, Declaration of independence can only be independence from Japan. This is the only way.
In the San Francisco Peace Treaty, 2a and 2b are identical, except in 2a Japan recognizing Korea’s independence (from Japan). The rest of the text is identical word by word.
But as of today neither Japan and Taiwan has the wisdom to spend advertising money to point out the obvious.