There are several things that I don't get in what you said.
You said that African populations were sometimes assimilated into larger regional governments or empires, then you said that those "weren't rooted in actual government structure". What does that mean? You said they were instead "rooted in religious or spiritual power or relevance, or rooted in economic power". Admitting this is true (easily dismissable for several of the most known African empires, but let's pretend it is), how is that related to having a "government structure" or not? How does that prevent them from being empires?
Could you expand on the fact that you don't believe West Africa had Kings nor royalty? What disqualifies the rulers of what we commonly (probably mistakenly according to you) refer to as kingdoms from being Kings, in your opinion?