did any black africans actually immigrate to the USA in the 20th century prior to world war 2?

Answer 1

A very small number--but it is impossible to tell how many would have, because between the turn of the century and 1965 there were strict, racially-based limitations on immigration. Thus, most of the Africans who came to the US came as students or workers from a European colony, and did not settle in the US permanently.