I'd be interested to see if anyone can come up with a productive response, because I honestly can't think of one. I can't see much of any incentive for African immigrants, be they African Americans or those from Africa itself, to travel to Latin/South America. They'd face discrimination similar to (if not worse than) what they saw in their homelands, likely have to learn a new language and integrate somewhat into a new culture. The Africans already living there may or may not embrace them, but I tend to think that they wouldn't, in a fashion similar to the disconnect between African Americans and their relatives from the home continent. Other than as a cheap source of labor, which could already be found within most of these countries (especially Brazil, which kept slavery around later than many), there wouldn't be much practical use for them.
The only thing I can see that might work, and i'm not sure how you arrive there, is to have Africans already in these countries be granted Civil Rights earlier on and treated more equally. If the government(s) made it a priority to uplift former slaves, giving Africans better social mobility, you might see some immigrants taking note and deciding to make the trip. But that strikes me as quite a longshot.