I think they are taking China's concerns seriously. That's why they are arming Taiwan.
I'm tired of this idea that the people of a region shouldn't have the choice of whether or not they are a part of a country. This applies to Taiwan, Ukraine, Chechnya, Palestine, Catalan, Tibet, or anyone else that wants to break off from a country people other than them decided they were a part of.
Some of the states suceeding might actually be a relatively peaceful way to get beyond the current political divide in the US. Though both of those states (and most of the others) are more purple than red or blue, so it's complicated and would probably require a mechanism to separate from the separation, kinda like West Virginia breaking away from Virginia when it broke away from the USA. All or nothing referendums probably aren't a great way to do something like this.
Honestly, I think the closest parallel to Taiwan in the 2020s is Cuba in, say, 1980s.
Their biggest sponsor is retreating from the world globally and can no longer really afford to support a full military detachment there indefinitely, especially after fucking up in Afghanistan for the last decade. There's a ton of economic reasons to just drop this bullshit and be normal, but they're too prideful to let the issue go. All their neighbors are increasingly hostile to the jilted-ex attitude their neighbor is displaying, but when you've got nukes who is really going to argue with you?
So the US perpetuates a blockade of the island for the next 40 years out of spite, hoping that one day the Cuban government will just kinda collapse and let the Americans back in.
And the Chinese will continue to economically love-bomb Taiwan, while picking fights with the US by running military drills around the island's edges, hoping against hope that they'll eventually get a better reception in Taipei than they did in Hong Kong.
If they honestly wanted to leave Ukraine to join Russia, I don't think Ukraine should stop them. But a) it complicates things when a country sends its own people to get a region to vote to join that country, b) it's also further complicated when there's a divide in the population (which also likely applies to the regions I mentioned), and c) I don't trust a referendum run by today's Russia after it invaded and displaced populations in those regions.
But yeah, I don't just believe this when it's politically convenient, though I would prefer to see such a mechanism used to enable self-governance rather than leaving one country to join another as ultimately I am anti-empire.