Ugh, a long comment got deleted, so I'm reconstituting here. I'd suggest /r/AskAnthropology ; they'd know an awful lot more I think. Chris Ehret says a fair bit in his Civilizations of Africa (2002), but that's about the deep past and has a fair bit of speculation. He uses Greenberg's classic linguistic groupings, four families (plus Madagascar!) that have certain tendencies to share features. The northern one, the Afrasan grouping, includes the origins of three world religions (Islam, Christianity, Judaism) so one might argue that quasi-African religions do in fact exist throughout the continent. Certainly they've been localized very heavily by African spiritual beliefs and practices (syncretically).

I can speak to one grouping, the largest. Niger-Congo (A and B incl Bantu) societies tended to have a common belief in a creator god, a somewhat henotheistic (you have your local deities, we have ours, each recognizes the other) system of demigods or territorial spirits, and ancestral spirits whose wisdom or voice could be tapped by various people (not actually worshipped as a rule). There's no clear set of boundaries for such beliefs; towns could be over 200 people, and exist in clusters or even kingdoms of similar belief, while spirituality and religion were not distinct categories in daily life but suffused society, culture, politics, economy, and everything else. (They often still do.) So yes, nearby spiritual orders would be similar or at least in communication; only where you have a jarring break between heritage areas owing to migration, etc., might there be clear distinction. But the similarity in some features (distant creator, importance of kinship, etc) gave great adaptability to these societies in incorporating other elements of religions that were complementary or at least not contradictory.

A few have become more widespread. Ogun, the West African (Yoruba) demigod associated with the spiritually powerful caste of ironworkers, kept its adherents even when enslaved or converted--and in fact there's a lot of fusion between Christianity and Ogun in diasporic religious practice today. (See Sandra Barnes's edited volume Ogun: Old World and New.) Tongnaab is another, from northern Ghana, which grew in reach and appeal from its original area because of its connection to security and power in the face of colonial domination and the seeming proliferation of witchcraft (or accusations)--so it's now a much broader deity with adherents outside the original territorial extent of the communities. People do not see these things as necessarily incompatible with Christianity, so I'm always a little confused by the numbers. (see Jean Allman's co-edited Tongnaab on this.)

There are of course a few creation beliefs and spiritual orders that undergirded certain states: the tracing of Yoruba (and a few other) polities to Ile-Ife, where Olorun (one of three manifestations of god, in this case the ruler of the heavens instead of the creator aspect) lowered the first king, Oduduwa, to Earth. That connection covers millions of people today, though it's not always a primary spirituality. There's also the Asantehene's Golden Stool, which came down from heaven to symbolize the spirit of the nation--although they do not name its provider, it is understood to be that distant heavenly ruler. Again, although this spirituality is not the stated religion of a lot of people who identify with Asante, it's respected to various degrees. But one could well argue that any state required a ruler to have certain extraordinary powers that accrued to their positions; this was true even in the Muslim leadership of a state like Mali, where the rulers also needed to be able to intercede with ancestors, negotiate with various castes (gold and iron in particular), and connect with rural populations who were almost entirely non-Islamic before the late 1600s (or later).

Good God, this is rambly. I'm sorry if any of it is dated or just improper in its characterization, although I am aware of the flaws of such generalization and the Greenbergian divisional system itself.