Show me in traditional African music anything resembling Jazz, Ragtime or Blues: it does not exist. The rhythms of early Jazz can already be heard in Anglo-Saxon operettas of the 19th Century. It is true to say that there have been some magnificent and even revolutionary black performers of Jazz, though more rarely in Rock'n'Roll with the possible exception of Chuck Berry. What is undeniable is that whites have promoted all phases of its evolution.
Rock'n'Roll is rhythmically-augmented Scotch Irish folk. Rock'n'Roll was blacks doing an impression of hillbilly music rather than hillbillies doing an impression of "black music". This is why white rock bands that follow just sound really white, because it's already deeply white going back centuries in its folk heritage. Even the supposed "blues notes" and tonalities come straight out of Scotch Irish music.
Musicologists tend to ascribe some unique quality to African rhythm when it isn't there. The difference between African and Western music isn't in the rhythm, but in the focus on percussion. African music is tribal and meant to be accompanied by dance. Primitive music in all areas of the world started as highly percussive because that's what comes readily to us as human beings. Western music had centuries of development and went astray from those percussive roots long ago.
While Western music was exploring dissonance after entering the modern period, blacks in America started using Western theory and instruments to return to basic human impulse: the rhythm. Turning the focus towards percussion exploded in black music's popularity because Western art music became inaccessibly experimental and dissonant to general audiences. Jazz and Blues's percussive focus caught on hard because rhythm comes to us instinctively.