Im watching this Korean + Vietnamese collaborate song. This is future music. A song is sing with two languages.
Does that means Kpop/Kdrama = Chinese + Korean + Japanese? East Asian refers to similarities in culture not the same culture. Each culture has its unique and differences.
Speaking about Similarity I believe Vietnam also has similarities (not the same) why Vietnam is not included? It is because the Chinese motive is linking developed countries such as Korea and Japan while axe out Vietnam because Vietnam simply poor country. Chinese consider Vietnam as South East Asian because, the Chinese thinks SEA = poor, backward while East Asian = developed and that included China, (though the fact China is not developed, is developing instead).
See how bias and racist and shameful Chinese is? Funny thing, Japanese does Not want to link with China nor Korea, Japanese look down on both Korea and China.