https://www.nps.gov/ethnography/research/docs/ggsrs_book.pdf
II think that people think that because Nigeria exported a lot of slaves then those slaves must have ended up in America. What people fail to realize is that the USA did not import that many slaves. Nigerian slaves went mostly to the Caribbean nations and South America and we know this because the Yoruba people still practice Santeria in those areas.
The only Nigerian slaves brought to the USA in any significant numbers were Igbo people. That is misleading too, because a lot of times it was not Igbo people being exported out of the Bight of Biafra; but it was Tikar people (Bamoun and Bamilke) of Cameroon and Kaba people of Chad.
The largest block of slaves brought to the USA were from the Kingdom of Mali (modern countries of Mali, Sierra Leone, Liberia, Togo, Benin, Burkina Faso, Guinea, Gambia, Senegal, Guinea-Bissau and northern Ivory Coast, Ghana, etc.). That is why people always joked that African Americans were big Mandingos; because most African Americas are descended from the Mandinka people. That is who Alex Haley traced his roots back to in Roots.
The other large group that African Americans come from is the Kingdom of Kongo (Angola, Republic of Congo, Cabinda, Democratic Republic of Congo and Southern Gabon). Another large group of slaves came from the Akan people of the central and southern region of Ghana and the Ivory Coast. This group was traded due to the rise of Ashanti. The Ashanti forced tribes around them to pay tribute. Tribes could either pay in gold, which is what the Ashanti wanted; or the tribute paying states could pay in slaves. Some tribes paid in slaves, which meant that they had to raid neighboring Akan people like the Brong in Central Ghana and Baoule people of the Ivory Coast. The Ashanti sold the slaves to the English. The English acknowledge that the Ashanti were not slave traders and the Ashanti were clearly not trying to sell other captured Akan people. The Ashanti used the slaves to work in the Gold mines, which is what the Bonoman Empire (Ashanti, Brong, Baoule etc) was all about; but later when the English asked to buy some of the slaves the Ashanti sold them. Btw, Ghana apologized for Ghana's role in the slave trade.
GHANA APOLOGIZES FOR ITS ROLE IN SLAVE TRADE: Countrys 50th anniversary includes tourism campaign