When the Taiwanese people democratically declare they want to become part of China. I don’t see the US sending military aid to China as long as their claims to the South China Sea don’t respect international maritime law. I’d also imagine respecting intellectual property rights is a concern, in addition to China’s genocidal actions towards the Uyghurs.
The Donbass and Crimea are currently occupied by Russia, there’s never been any Ukrainian held election allowing for the secession of this territory. These regions are not self governing entities that can make this determination. With all due respect, you seem a bit dull, so I’ll just leave it at that.