Why is the United States government supporting Taiwanese sovereignty despite its own anti secession laws?

The People's Republic of China, according to many reports, is considering invading Taiwan. There is a law on the books that says if Taiwan does not bend diplomatically they will try to make it part of China by force.

Why is the United States coming out in support of Taiwan given its own laws would stop a state, say Texas (the state that has the most talk of independence and was once even its own country), from declaring independence? The fact that the United States is supporting a country which could be argued to have seceded while the US explicitly does not allow its own states to become its own countries seems hypocritical. And also though I focus on the USA here, this question is not specifically about the USA. It is also about all countries with anti secession laws that are supporting Taiwan.

I'm not privy on the details. But I do know China and Taiwan are in a tough relationship. This question is not designed to criticize any country's positions. It's just for curiosity. To be clear I personally support Taiwan's right to choose on its relationship with mainland China. But, I'm pointing out something that others may see.