Going back to the OP, and momentarily forgetting the “how,” if the US extirpates their Black population, US popular culture and therefore global popular culture would unfold completely differently, because all American music is Black music. Blues, Gospel, and Jazz have already been created, but might have difficulty enduring in a music scene made entirely of white musicians. Ike Turner had not yet written the first Rock and Roll song at the time of the POD. Enclaves of Black music might take prominence globally from other diaspora capitals, like Paris, or from within Africa. But if the US unfolded in the same way as a cultural juggernaut, but without Black cultural influences, it would make for a much whiter and blander global pop culture.