1. How the PRC (mainland China) regards Taiwan (or ROC).
2. How Taiwan regards itself. This has changed over time.
3. How third-parties play that situation.
Since Nixon's visit to China in the 1970s, the world recognized that it was pointless to deny that the CCP (Chinese Communist Party) ruled mainland China for good. From there, the PRC progressively got official recognition in institutions like the UN. In order not to inflame the PRC's leadership and keep access to mainland China, many countries state that they do not recognize or encourage Taiwan's independence. But note that they also maintain de facto diplomatic relationships, being careful not to use the name "embassy" or "consulate".
In reality, Taiwan has been absolutely independent since the 1950s. It's just that it's not officially recognized by most institutions and countries for diplomatic reasons.
I'll add that the "one China policy" is ambiguous by design. It doesn't mean that it must happen in the foreseeable future. It also doesn't mean that the PRC should be allowed to take over Taiwan through military might.
In the end, no matter what the various parties' policies are, almost nobody in Taiwan at this point believes that a peaceful so-called "reunification" is desirable or possible. I put the word "reunification" in quotes in particular because the CCP never controlled Taiwan, and also because in general the historical argument doesn't make any sense. Personally, I think that the principle of self-determination is what should apply here, for moral reasons. [1]
What you say is true, and I agree on self-determination in the abstract. But I simply can't believe the U.S. is in Taiwan to defend its people, rather than contain and weaken mainland China. The U.S. has demonstrated time and again it will gladly throw an ally under the bus in order to weaken an adversary ("it may be dangerous to be America's enemy, but to be America's friend is fatal"). To go back to the OP, moving TSMC to the U.S. looks a lot like preparation for scorched earth in Taiwan. [1]
1. How the PRC (mainland China) regards Taiwan (or ROC).
2. How Taiwan regards itself. This has changed over time.
3. How third-parties play that situation.
Since Nixon's visit to China in the 1970s, the world recognized that it was pointless to deny that the CCP (Chinese Communist Party) ruled mainland China for good. From there, the PRC progressively got official recognition in institutions like the UN. In order not to inflame the PRC's leadership and keep access to mainland China, many countries state that they do not recognize or encourage Taiwan's independence. But note that they also maintain de facto diplomatic relationships, being careful not to use the name "embassy" or "consulate".
In reality, Taiwan has been absolutely independent since the 1950s. It's just that it's not officially recognized by most institutions and countries for diplomatic reasons.
I'll add that the "one China policy" is ambiguous by design. It doesn't mean that it must happen in the foreseeable future. It also doesn't mean that the PRC should be allowed to take over Taiwan through military might.
In the end, no matter what the various parties' policies are, almost nobody in Taiwan at this point believes that a peaceful so-called "reunification" is desirable or possible. I put the word "reunification" in quotes in particular because the CCP never controlled Taiwan, and also because in general the historical argument doesn't make any sense. Personally, I think that the principle of self-determination is what should apply here, for moral reasons. [1]
[1] https://en.wikipedia.org/wiki/Self-determination