Genetics play a role in the 15 point black-white IQ gap in the US. Chances are, they explain almost all of it at this stage, while the larger 30 point gap between blacks in Africa compared to whites in Europe/USA likely still has a significant environmental component (probably 20 points to genetics, 10 points to environment).

Reasons:

1. Enormous environmental difference required to entirely explain the IQ gap given high heritability of IQ
2. Transracial adoption studies
3. Blacks of high incomes scoring lower than whites of low incomes