Wait, do you really think president Moon of S. Korea is ethno-nationalist of all things? You have no idea what you're talking about - he's just your run-of-the-mill liberal.

You really need to be careful generalizing the whole Asia region to fit your narrative. S. Korea was already a bit culturally ethno-nationalist not because of reasons like 'racism' or something like Western populist politics, but because of the more complex history of being colonized and almost assimilated by Japan. And diplomatically S. Korea's has always been pro-US for pragmatic reasons (military protection) and would probably stay that way for some time. (That doesn't mean there isn't any anti-US sentiment among citizens, it's just that it hasn't been materialized into anything significant in actual global relations.)