My comments here and elsewhere generally have to do with the present century, but I do understand the appeal that history holds for many of us, especially when casting about for our "what abouts". One thing we can agree on is that the U.S. has been very consistent in doing what it's politicians sold as being in its best interests. Sometimes it turned out that its actions were not in its best interests.
when I read this my first thought was that it did not jive with what I recall happening, but it's been years and my memory was somewhat hazy. So I took the time to look up the details. In truth the U.S. made numerous, valiant attempts to protect Taiwan's representation in the UN but was repeatedly out voted. It's always good to keep our facts straight. You may be too young to recall that as a result of civil war in China, Maoist forces pushed the army of the then official government of China, the "Republic of China" or ROC, out of Beijing and the government's army then retreated to the island province of china known now as Taiwan. The U.S., however, continued to recognize the government of the Republic of China as China's legitimate government, even though that government was now in exile. Subsequent events led eventually to UN Resolution 2758 passed in 1971, which recognized Mao's revolutionary government as the official government of China and removed Taiwan from UN representation. The U.S. voted against this resolution, of course. The U.S. had favored instead that both the PRC and the ROC be represented at the UN as two separate countries. Your recollection was perhaps formed during childhood exposure to revisionist history. Which does happen. For every detail and all of the votes leading to Resolution 2758 see: https://en.wikipedia.org/wiki/United_Nations_General_Assembly_Resolution_2758
"... And the U.S. Department of State informed the Senate that "[t]he United States takes no position on the question of Taiwan's sovereignty." The U.S. Department of State, in its U.S. Relations With Taiwan fact sheet, states "[T]he United States and Taiwan enjoy a robust unofficial relationship. The 1979 U.S.–P.R.C. Joint Communiqué switched diplomatic recognition from Taipei to Beijing. In the Joint Communiqué, the United States recognized the Government of the People's Republic of China as the sole legal government of China, acknowledging the Chinese position that there is but one China and Taiwan is part of China.[67]"
The U.S. has always honorably fulfilled any binding obligations with regard to Taiwan. The current position of the U.S. is detailed here: https://en.m.wikipedia.org/wiki/Taiwan–United_States_relations# Despite the U.S. having formally recognized the People Republic of China it maintains cordial, informal relations with The Republic of China as well.
We are not talking about obligations here, you are tilting towards different issues. We are talking about working with one government /nation one day, and causing it harm the other when it differently interprets its strategic interest tomorrow. Persia, Taliban, Kurds, Afghan people, Nordstream, Vietnam,...
I had always found it interesting, from an outsider of the US. When the US was supporting terrorism against Russia, they referred to the people they gave money, arms, and combat training to as 'freedom fighters'. Yet when it turned around and bit them in the ass by 9-11... Suddenly the same people were renamed from 'freedom fighters' to 'terrorists'. And ironically, it was Russian weapons now being supplied to the SAME people that the US was supplying weapons before! Funny how the universe works out...