So when a colonized country becomes unable to govern for a 40 year period a territory that was part of their nation for 400 years due to the colonial intervention and destabilization of their state they should just accept it as a break away country.

That's the case with Tibet and it's "sovereignty" from China in the first half of the 20th century . And to be clear even then almost no country on earth recognized Tibet as a sovereign country and as NOT part of China. And that's not to mention Tibet being a horrible slave theorcracy

You are talking nonsense and implicitly support the balkanization of China by colonial intervention. Literally investigate the relevant history before pretending to have informed takes