While Taiwan is not "officially recognised" by most of the UN that does not make it a part of China they have their own institutions elections military and other stuff unlike Abhkazia and South Ossetia who rely on Russia
The USA did not intervene in the Chinese civil war cuz no country thought that Nationalists would have lost Communists were weaker than Nationalists but you never know what life will bring you. I am kind of hoping that Xinhai Revolution happens again that mainlanders have enough of the CCP and it's corruption and human control policies