The Sino-American Mutual Defense Treaty was nullified over 40 years ago. The US policy with respect to Taiwan since then has been strategic ambiguity, and we can see how well that worked out for Ukraine! They were in the same situation as Taiwan, being strung along by US assurances without a firm commitment. The parallels are obvious, and if I were a Taiwanese policymaker, I certainly wouldn't be counting on US military intervention.
Also refer to multiple occasions this year where Biden has said that the U.S. commitment to Taiwan was similar to NATO Article 5, or otherwise that the U.S. would militarily defend Taiwan:
Compare that with ... nothing at all of any similar kind of legislative or executive message w.r.t to Ukraine. There is no strategic ambiguity about the U.S. defending Ukraine military; the U.S. is absolutely not committed to that course of action and has never been - the strongest language on this point being a non-binding memorandum from 1994.
I'm familiar with the Taiwan Relations Act, which means I know that it provides absolutely no guarantee of military intervention. What exactly is the relevance of the Taiwan Relations Act to the question of whether the US has guaranteed military intervention if China invades Taiwan? You are citing an irrelevant current law, and a treaty that expired 40 years ago, which doesn't inspire much confidence in your subject matter expertise.
As with Taiwan, with respect to Ukraine the US did not guarantee military intervention, but reserved the option to intervene and made statements to that effect. In recent months, they did clarify that they would not send US troops to intervene directly, but I expect we would see similar statements from the White House if China started preparing for an imminent invasion.
The opinion piece that you linked spends the first three paragraphs explaining why people should believe that Biden's statement wasn't a gaffe. That opinion piece was published on May 25. The Fox News story describes how Biden walked the statement back on May 24. Apparently the author either didn't bother to follow the story for 24 hours, or just hit publish with out of date info. Either way, rather embarrassing.
You clearly aren't here to engage in good faith discussion, so I'm done.