Tibet? Taiwan? Vietnam? South Korea (by proxy)?
[I should note that I find these types of discussions useless in the first place. No problem among living humans was ever solved by arguing over whose ancestors were less barbaric...]
If you think about it like this it explains everything that the government has been doing for decades. They limit the population growth so that they can feed everyone and keep discontent down. They focus on the economy to keep discontent down. They build regional and world status to create pride in a greater, unified China. Even their tv shows and movies glorify themes which show a united China as one, and always the government are the good, humble servants. Military power, technological independence, even hostility towards other countries is mostly to build patriotism and unity among their own people.
And of course they restrict the internet, control the media, and limit what people can see and say.
Even when China was being successfully invaded by the Japanese, the existing government was more concerned with the Communist revolution. When they finally got desperate and banded together with the Communists to fight the Japanese, they lost ... to the Chinese Communists who took the opportunity to overthrow them.
So in that sense, it is helpful to understand the Chinese government and the things they are likely to do, and how to interpret them.
LOL! Tell this to Vietnam, Philippines, Mongolia, and most of their frightened neighbors.
They were later Sinicized after several generations.
So is the common believe of a group of people enough? Or does it need the recognition of others?
Partly, it depends on whether the debate over nation status is a merely one of linguistics and categorisation or whether we're making ethical arguments.
When Japan annexed Korea, did the Korean people cease to constitute a nation? When Japan annexed Taiwan, did Taiwan cease to rightfully belong to the Chinese government of the time?
(As an aside, I think that no-one talking about the Taiwanese company's involvement in IP theft is a pretty good example of how the press is incentivised to lead with a sensationalised narrative that inflames sentiments, how people focus on facts that fit a pre-existing narrative, and a general bias against China).
US biggest threat is the national debt and the unfounded and underfunded liabilities.
The national debt is really not a problem as long as the USD still the world reserved currency. How the reserved status may change because of China and that’s the real threat.