- Kelly Clarkson, Trisha Yearwood, Florence Welsh, Amy Lee, Adele, Christina Aguilera, Jojo & Hayley Williams are all considered great singers.
- Most women that sing opera or on Broadway are white.
- Charice (I know, she's a man now) is Filipino.
It's probably because pop music looks for "soulful" voices. That's why all the white girls in pop music that are known for singing come from humble beginning and soul-influences.
Among African Americans, the soulfulness originated from the days of slavery when Blacks would sing hymns to each other. Their music evolved, and eventually, white people adopted soul music into rock & roll and it expanded from there. But african Americans are the originators, therefore "better" at it.
And there is the tea.
But outside of popular music (opera/broadway, middle eastern, chinese monks, etc), they are not the best.