Texas and Taiwan share very little in common in terms of history as political states and entities in the world economic system. It's a strange analogy you're asking us to make with negligible equivalencies.
What Texas and Taiwan share is that they're both territories of sovereign nations. US has no business interfering in the internal politics of other countries. It's that simple.
US State Department acknowledges that Taiwan is par of China in black and white:
The United States approach to Taiwan has remained consistent across decades and administrations.
The United States has a longstanding one China policy**, which is guided by the Taiwan Relations Act,
the three U.S.-China Joint Communiques, and the Six Assurances. We oppose any unilateral changes
to the status quo from either side; we do not support Taiwan independence; and we expect cross-Strait
differences to be resolved by peaceful means.
You keep quoting this, seemingly without reading it:
From the "Six Assurances" mentioned right there:
> The United States would not formally recognize Chinese sovereignty over Taiwan.
Additionally, the "Taiwan Relations Act" (again mentioned right there) says:
> The act authorizes de facto diplomatic relations with the governing authorities by giving special powers to the AIT to the level that it is the de facto embassy, and states that any international agreements made between the ROC and U.S. before 1979 are still valid unless otherwise terminated.
(noting the that Postdam treaty you mention elsewhere was made with the ROC government because it was in 1945)
> The TRA provides for Taiwan to be treated under U.S. laws the same as "foreign countries, nations, states, governments, or similar entities", thus treating Taiwan as a sub-sovereign foreign state equivalent. The act provides that for most practical purposes of the U.S. government, the absence of diplomatic relations and recognition will have no effect.
US State Department acknowledges that Taiwan is par of China in black and white:
https://www.state.gov/u-s-relations-with-taiwan/