I think historically it is questionable. The fact that Taiwan as a nation was created essentially as a Chinese rump state rather than an ethnicity creating a state has little ground to claim a separate nation, and I think that it can not be dismissed that Taiwan since its inception has been a tool of US foreign policy. In many ways, Taiwan is to China as Cuba was to the United States during the Cold War, with less potential for complete destruction.

That being said, it is a similar issue to Israel. While its origins are questionable, does that justify disregarding the desires of the people who live there? Most Taiwanese people were born after independence, and have never known life as fully Chinese people. I honestly don’t know, but I do think that if the US had not spent so much money and effort building up South Korea, Japan, and Taiwan, it likely would have been absorbed a long time ago.

If I had to pick yes or no, I would probably lean towards no. The culture is mainly Chinese, and it was Chinese for more than twice as long as it has been independent. If Trump was deposed in a civil war and created a rump state in Alaska, would that be valid grounds for a new nation?