There’s more to Africa's issues than the collapse of empires coming from the depopulation that came from slave taking and then European colonialism. Much of the continent is a plateau, so no water borne shipping going to ports upriver - so development had to wait for rail (much more expensive per ton/mile, particularly if there’s an elevation change). This left the areas where those empires had been disconnected and more susceptible to colonization — and lacking the wealth to build their own. And even now, with rail left behind by those colonial empires, labor is still 'stranded' behind this more expensive class of transport. On top of that, there isn't proportionally a lot of productive acreage (much in use needs amendments, which are imported and costly, varying with the cost of energy as the Haber process is quite energy intensive). Add in unreliable precipitation and you have a recipe for food import dependency. And global warming is on track to make that precipitation even less reliable. Most of us (including me!) have a difficult time wrapping our heads around how BIG Africa is. And it's N-S big so a range of latitudes, each with a different clime.
Add in legacy from first colonialism, then decolonialism (part of the US’s push during WWII was to get empires to disgorge colonies, the idea being that the US would protect blue water trade so any country could trade with any other). That worked for much of Asia, but Africa had that vertical issue (no direct ocean trade) — and they’d been abandoned by their former colonial empires. Then there was the Cold War, which distorted, well, everything. The richest nation on the planet (thanks to geography pretty much the opposite of Africa) was in a panic over ‘communism’ taking over the world. That opened the door for corruption. All a leader had to do was declare himself “staunchly anti-Communist” and the money flowed. Far from our finest moment.
OK, so immigrants. We in the US have a legacy of slavery, then Jim Crow, then discrimination to deal with. Chattel slavery was possible because Africans did not look like Europeans, which allowed for the idea of ‘race’ — and both superior and inferior ‘races’. (I grew up in New England, was shocked speechless the first time I saw “whites only” signs.) Immigration-wise, the issue seems to be (like with ‘races’) that immigrants are visually different from the present inhabitants. They may not be native speakers of the local language. What Europeans and Americans don’t seem to understand is that we are in demographic collapse (America less than Europe as the WWII generation here did have kids) and desperately need incoming young people. I’d get into that, but this is more than long enough for a response… :-)
