Nope, you're just conflicting history, international law and recognition, and perception of the
current situation. You can't talk about "familiarity with history" and "but today". Precisely because the history is so complicated the "today" is too.
How is Taiwan totally different? The Kuomintang lost the civil war, and ran away to Formosa/Taiwan, where they assimilated the local population by not always nice means. (The comparison with Hawaii is valid only in an alternate universe where the CSA run away there and just continued to exist.) There was never a peace treaty, and up until very recently the ROC still pretended to be "the one and only China". They don't themselves claim to be an independent country, and aren't one de jure ( probably to a significant extent because they fear China's retribution if they do so, but still). As far as China and literally almost all of the world are concerned, Taiwan is an island belonging to China. The legitimate Chinese government is the PRC.
The de facto situation is that Taiwan is for most intents and purposes an independent country, and the "ideal" solution is for them to just become one, but China has no desire ( and why should they have it?) to just let go of something they consider theirs.
It should furthermore be noted that China has experience with temporarily ceded territory they retake after tens if not hundreds of years ( Hong Kong, Liaoning, Manchuria, Qingdao, etc.), so i don't think they see things as "this land hasn't been ours for X time, it's no longer a part of us".
