Korea is fairly unified. The majority of the population are survivors (or descendants of) the last major invasion that ended in 1945(-ish). There's two major dialects of Korean and a general unity of heritage because it's a small country and defended itself well.
China is not like Korea.
I'm not sure where I was going with this... but since China is in the news again, please stop treating it like the Switzerland of Asia. That's the wrong mental approach to China.