No kingdom in Africa was fully Christian, but the kingdom thats official religion was declared Christain was Axum.
The Kingdom of Aksum.
Aksum and Ethiopia
Axum
Axum
Aksum and Ethiopia
Kenya
jewish
Probably the Palestine region although it was not the official religion at the time.
Kenya
Many slaves adopted Christianity
The Kingdom of Armenia was the first state in Europe to adopt Christianity as its state religion. Armenia adopted Christianity as its state religion in 301 A.D. The Roman Empire was the second state in Europe to adopt Christianity as its state religion, and it did so in 380 A.D.
I think a better question would be what is the implications of Christianity on African traditions.