When Africans were brought over to America as slaves, they did not speak English. They only spoke African “tribal languages" the majority of the slaves were sent to southern states.
The white "slave masters" themselves did not speak proper American English. And matter of fact, the majority of white people living in the southern states did not speak proper American Standard English either.
The first group of slaves from Africa, who made it to America – the majority of them never, learned English. But their children did and their children were bilingual. They spoke "English and the African tribal language" that their parents taught them.