Regarding the rise of doubts in Taiwan about US military aid if China invades, I have the following response. The doubts are reasonable, assuming that a Chinese takeover is not an existential threat to Taiwanese.
It is not, though, a response I would expect to hear from a Korean, Vietnamese, Japanese or Ukrainian.
Some Taiwanese academics and politicians do not believe a Chinese takeover is a threat to Taiwanese, not because they do not believe a Chinese takeover is a possibility or a probability, but rather because they do not believe, in their hearts, that there really is such a thing as a Taiwanese people.