Keep, japan, u.s and south korea as the minimum and any number of countries as your max. Compared to the mainstream music of their country how popular is kpop?
You could include bts aswell but I prefer if one doesn't cuz in many countries it's solely just them, one group that's dominating. You could swap the words bts and kpop and no common layman would know the difference. That's not the rise of the kpop genre but just the rise of bts. So though they are a major part of the equation, keep them aside and tell me how dominant kpop is as a genre in various countries?