Honestly, "pop" in the USA has almost universally been crap with the occasional exception (like Michael Jackson). Pop musicians in the USA tend to take themselves way too seriously; they forget it's about entertainment, engaging their fans, and making people happy. Singers like Mariah Carey and Christina Aguilera get a little bit of early success, they let it go to their head, and then embrace the "diva" title, not realizing that "diva" is not always complimentary word.
Though, I have to honestly say I'm not super into a lot of the Pop music coming out of either Japan or Korea; it's at least tolerable, and some of it is really fun. I prefer the rock and pop-rock from there; that's more the style that I've always liked. It's interesting to see that similar light rock'n'roll music appears to be coming back into style here in the USA, though today they're packaging it as "alternative," for some reason.