Researches show that blacks in other countries have even lower IQ (85 in the US vs. 70 in Africa).
The reason behind this difference is the fact that the African Americans are an ethnically mixed group, while the African blacks are mostly pure-blooded people.
http://www.nytimes.com/2014/12/25/science/23andme-genetic-ethnicity-study.html?_r=0A recent study found that only 73.2% of the African American genes are black. A further 24.0% of the genes were European, and around 1% was American Indian. As a result of this racial mixing, the IQ level of the African Americans is more than that of the blacks in Africa.