I'm trying to put the best spin on this and assume he means that an identity just based on what color you are isn't a valid identity, but you're right, of course a huge influx of people with their own culture, history, and values will change the identity of the region, obviously that happens, there's no way for that not to happen

North Africa is largely Arab, not black, and historically was more closely tied to the Mediterranean world than sub Saharan Africa. Even though they're on the same continent when you look at a map, the giant desert might as well be an ocean since it acts as a geographic barrier, similar to how the Himalayas cordon off India into it's own region even though it looks like just another part of Asia if you're looking at a map with no context