Slaves "Africanized" the South by mixing African influences with aspects of contemporary American culture. Because whites mingled with the slaves, they picked up some aspects of that African-American culture.
Perhaps the most well-recognized aspect of Africanization is musical. The banjo and the bongo drum are instruments that were created through this mixing of cultures. Other musical influences permeated Southern culture and eventually led to the development of jazz.
In addition, there were other impacts in areas like food. Slaves were responsible for the creation of things like barbecue, fried chicken, the use of things like black-eyed peas and various kinds of greens.
By exposing whites to their mixed African/American culture, the slaves, to some extent, Africanized the South.