Warhead answered my question.
To Warhead,
Maybe you don't think so, but to me, Tibet and East Turkistan has never historically been an inseparable part of China.
Especially Tibet. It has NEVER been a part of China until the invasion of the Chinese red army.
Also Inner mongolia although less disputed, but isn't historically a part of China either. To best, China was a part of Mongolia.
And let's review to the Qing dynasty.
China had to sign a treaty to give Indo-China to the French. Was Indo-China ever part of China? Actually no. Vietnam had its king, all the other countries had their leaders. But to China, if they pay tribute to China, China had responsibility to help them.
That is why when Ryukyu was invaded by the Japanese near the end of Qing dynasty, the king of Ryukyu wrote a letter asking for help to the Qing's court.
As I said, you can't use today's view on nationalism to view international situations back then. Back in the days before European imperialism was introduced to Asia, things worked a little differently.
I mean if Zheng-He's fleet was an European fleet, with that amount of man power, could you imagine he just stop at each country and ask for trade and tribute? It was just a different set of rules and view of the world back then.