People don't understand why China does what it does. People also don't notice that China only cares about Hong Kong and Taiwan. Do you see them claiming Mongolia or Korea or any part of Southeast Asia? Hong Kong was originally China's before the British sacked them. It was never meant to not be a part of China and in accordance with the original agreement it would be part of China in the near future anyways. Taiwan was formed effectively from KMT defecting after losing.

A good equivalent for America would be if say if China came in and just took a major port city or any major city like LA or SF. Yes I'm sure America wouldn't want it back. Or if Confederates took a nice chunk of the population to the dominican republic/cuba plus dominican republic/cuba are more habitable.