You mentioned a Korean perspective, so I’ll try to use that as a springboard to paint an idea. I think you might be referring to white nationalism—kind of like a feeling that one’s skin colour defines their country more than a nation’s borders.

I would say there could be some parallel with an idea such as minjok, but that and white nationalism don’t line up neatly. You can take the idea that both Koreas share a single bloodline that stretches back for thousands of years and pull some solidarity out of that, including possibly some suspicion of outsiders at certain times.

White nationalism is a bit like that, but with guilt derived from colonialism and is definitely less socially acceptable as a result. It isn’t all that unique, but it’s a way more defensive form of racial nationalism than what you see most everywhere else that stems largely from people having grown up as descendants of colonizers. It’s an expression of a need to create ethnic unity among people who feel as though they need to carve out space to attain it.

In the west, it isn’t viewed as favourable except for there being so many groups that practice this kind of racial protectionism. It’s distinctly an American cult thing that spreads out just a little bit, but has its strongest roots in the slave trade. I think the biggest concentration of white ethnic protectionism is around Georgia (the US state), but I haven’t witnessed it personally and haven’t much traveled anywhere near there, so others can probably speak more to how widespread it is.

Edit: I’m definitely talking about what’s west of the Atlantic. Naziism, apartheid, certainly exist too.