The Taiwan Relations Act
Correct - there is no formal “obligation” to defend Taiwan.
Nixon and Kissinger were pretty sure we’d have open access to Chinese markets and were prepared to sell out Taiwan.
However, the language in the TRA 1979 is seen as strategically ambiguous, but the bottom line is near obligatory as you are going to get.
“The act further stipulates that the United States will “consider any effort to determine the future of Taiwan by other than peaceful means, including by boycotts or embargoes, a threat to the peace and security of the Western Pacific area and of grave concern to the United States”.
Diplomatically, “grave concern” is used as a use of force option.
The Taiwan Relations Act is not a treaty, and it does not promise defense.
You know as well as I do that a mutual defense treaty with Taiwan, if one were signed, could not be ratified by this or any conceivable Senate.