They never claimed to have a communist system to begin with. That is a western label placed upon them. Communist parties do not implement communist systems any more than green parties implement “green systems.” They implement socialist systems.

Comparing this conflict to “manifest destiny” is just complete brainrot and doesn’t make it seem like you are that interested in understanding the actual historical circumstances. This is an unresolved civil war due to the USA’s invasion to protect one side of the civil war, which in China is viewed naturally as a major attack to their sovereignty so allowing a foreign power to just cut a piece of them off is viewed negatively due to the Century of Humiliation of them being carved up by foreign powers.

Both sides also agreed to the reunification of China and this “one-china policy” became internationally recognized by almost the entire world, and it was not until the year 2000 that Taiwan de facto stopped agreeing with this policy. You can make an argument that Taiwan’s fairly recent desire for sovereignty should be respected without resorting to bizarre comparisons like Manifest Destiny, as this is obviously not what is going on for anyone who is intellectually honest about the situation at all.

This is not even an economic dispute and so trying to use Marxian analysis and throwing around buzzwords like “imperialism” is irrelevant. One of the biggest reasons the PRC hasn’t invaded Taiwan is because they would be harmed from the destruction of TSMC, so if anything economic reasons are discouraging the PRC form acting than encouraging it. The desire for China to reunify with Taiwan is a cultural and historical disagreement, it is more of an ego thing. They view the splitting off of Hong Kong by the British, Macau by the Portuguese, and Taiwan by the USA as attacks on their national sovereignty and thus to their national pride, and have vowed to bring them all back into the fold for decades now, and Taiwan is the only one left.

It is really an ego thing more about national pride. Again, you can indeed argue that they their national pride shouldn’t override Taiwan’s right to self-determination, but it is not as deep as you make it out to be. If you read some of those Marxian books you would find that invasions for “imperialism” is supposed to have the goal of expanding to new markets, but China is already Taiwan’s biggest trading partner by miles, they already dominate their market.

You are trying to make this way deeper than it actually is. This is about one state’s ego and national pride vs another state’s desire for self-determination. It is not some deep analysis over capitalism or socialism or imperialism.