Trade and finance
Africans can expect a cessation of normal financial and economic relationship with the US, a major development partner if the country goes into war. US economic mobilization would be geared toward war efforts.
Such a scenario would mean the financialization of many African plans may come from elsewhere. China comes to mind but a war involving the US would not necessarily benefit Chinese who have billions of dollars in investments States-ward.
The EU and other major partners would also not be so inclined to help.
Oddly enough, a WWIII is a weird opportunity for Africans to have the trade and financial relationship they have been postponing for half a century.