Except you were trying to mean a Nigerian contesting for the president of America and of course it is the Nigerian religious bigots that will vote a Nigerian as the president of America.
However, talking of black man being the president of America, there have been Barack Obama as African American black president and Kamala Harris as vice president.
I don’t know about Nigeria, but when Barack Obama was contesting, his support came mostly from blacks. Right? The whites hated him (till he left) just because he was black and many blacks liked him because he was black. I know certain people liked him because they knew he was a capable president, however, most of the votes, likes, and dislikes were based of on factors like what I just described which isn’t the real thing to be worried about. That’s what I mean.