Given the demographics and the difficulties they deal with, I think it's amazing that the people of some village in Africa even know much less give a shit who the President of the United States is. I certainly can't name an African president off the top of my head, with the possible exception of Zimbabwe, South Africa, Egypt, and Morocco. I know who the Archbishop of Nigeria is, but that's because I send him hatemail.
The reason that you don't know who is in charge of most African countries is that they don't project power outside of their immediate spheres of influence, don't provide security for their allies, don't send aid throughout the world or otherwise influence events. They know who is in charge in the US because they know who sends them aid, who brokers the peace when they finally stop fighting with each other and who leads the rest of the world into the future.