Be careful not to box yourself into a concrete search term for your topic. Think of synonyms for your subject - broader terms, related terms, and narrower terms. Using this strategy will guarantee a wider selection of materials. Be aware, too, that some search terms may be uncomfortable to think or say out loud - but could yield possible results.
"African American" is a broad ethnonym that doesn't even begin to capture the myriad experiences and diaspora of African peoples, both here in the United States and elsewhere. Take a look at winners of the Coretta Scott King Award as an initial search and for keyword ideas.
Possible search terms: Black, Black American, Civil Rights, Black Lives Matter, Ghana/Ghanian, Congo/Congolese, race relations, African Americans--social conditions, apartheid