Yeah, and most Americans, Canadians, and Australians don't consider themselves European colonizers, but they don't get to decide to that, because history matters. The Han Chinese living in the province of Taiwan are Han Chinese. They are of the Chinese nation, and they have never been otherwise. They have never seceded from China.
Are you saying that the people of Taiwan have a right to secession? From where does that right derive? The Confederates didn't have a right to secession. Texas doesn't have a right to secession. Quebec doesn't have a right to secession. In pretty much every context you can think of, a secession would cause a civil war.
But imagine this: a secession with a geopolitical enemy providing massive military support. Do you think that if China came to Canada and built up a military presence in Quebec to protect their secession that this would be a totally valid thing to do and Canada should let them? Do you think the Chinese navy is allowed to encircle Hawaii and help them secede from the US and that if the US tried to stop them that would be beligerence?
No. Of course you don't think those things. You only see the narrative of Taiwan from the West. You don't see the military reality of 70 years of US military intervention and support for fascist dictatorship. You don't think through the implications of what 40 years (3+ generations) of violent mass murdering fascist political persecution for desiring reunification did to the population of Taiwan (hint, it skewed public opinion pretty dramatically for their own self preservation).
You don't even realize that Hong Kong and Taiwan were transitioned to liberal democracies at almost the exact same time, and only a few years after South Korea was beginning its transition, coinciding with the clear signs that the USSR was collapsing and the threat of global communism was coming to end. The US and UK administrators of these territories decided that they didn't need to worry about communism anymore so they allowed the transition to liberal democracy to occur. If it was going to be too dangerous, they would have kept supporting the dictatorship and colonial administration and supported the violent repression of protests, like they had been doing for decades.
The people of Taiwan province do not have a right to secession and the US does not have a right to militarily defend their secession. Taiwan has never stopped being a province of China and just because the world's most psychotic, beligerent, genocidal military is trying to tug at your heart strings with stories of resistance and democracy, the reality is that you wouldn't support this configuration in literally any other context.