A great collection of essays can be found in the book "Ancient Egypt in Africa by O'Connor and Reid.

It seems that you have some knowledge on the subject because, although we don't see any conclusive archaeological evidence of continuity in most other african peoples, we do see some similar cultural elements that pop up.

Nubia, the culture that Egypt had the most contact with, was culturally distinct until about 1700 BC. At that time, the Egyptianization began to set in to the point that the Napatan-Meroitic culture was very Egyptian in form and content. O'Connor's essay talks about this, and then goes on to mention that the culture still remained distinct despite that assimilation. For instance, they didn't adopt the intensely bureaucratic system of government that Ancient Egypt was famous for.

Some, like David Wengrow of the UCL Institute of Archaeology, discuss the relation between Egyptian Kingship and that seen in other parts of Africa. Some of cultures seem to share the royal ceremonies focusing on "the King's body and displaying his active role in binding the inhabited land to an ordered image of the cosmos."

Unfortunately, the subject (like many Africanist subjects) doesn't get a lot of discussion/research.

As I posted above, the best source is that collection of essays. Besides that, and for a more focused discussion, see Prof O'Connor's book on Ancient Nubia.