I'm something of an overdeterminist, but I really think that Africa was as good as it was going to get. A post-1900 PoD isn't gonna solve anything. Now before you all beat me up for speaking against alternate history on AH.com, let me defend myself.
Let's talk about borders to start. We already know that Africa's borders don't make sense form an ethnic standpoint. But what about from a literal survival sense? There are tons of African countries that are literally stuck in "death borders." Niger. Mali. Chad is I think the most horrific example. These countries are mostly desert, and in Chad's case is literally turning to dust because it's lake is evaporating. If you look at pre-Colonial African states like Mali or Songhai, they were based around rivers and trade routes. The landlocked states of the Sahel are based on madness; there is no way to look at a lot of those borders and think "man this country is gonna be a real heavy hitter some day". And Africa is
full of countries with these death borders, struck with awful (mostly landlocked) lands that can barely sustain their population. And even those countries that aren't landlocked, a lot of them are just insane, border-wise.
The Gambia, anyone?
And lets move on to the trials of being landlocked. As is well known, being a landlocked country is pretty much being
set up to fail in most cases. Once independence was reach continent-wide, Africa found itself with a record-breaking
fourteen landlocked states (which would become 16 when Eritrea and then South Sudan won independence later). As if that weren't bad enough, European colonialism absolutely destroyed Africa's internal trade routes by erecting barriers between colonies and forcibly reorienting trade towards the coasts, which impoverished once thriving internal regions. So not only was Africa saddled with desperately poor landlocked (and non-landlocked) countries, it could not hope to uplift them through trade since Africa's economy was so completely orientated to exporting out instead of trade within. To this day, many if not most African countries still list non-African countries as their biggest trading partners, while those same non-African countries do not count the African ones in the same way.
Africa is a continent that rather than hitting the ground running, it broke both its legs and had its hands tied together. And once you add in the Cold War, well, the rest is history.
So, PoD's. If you want to change the borders, the question is how. Do you draw borders along ethnic lines? Then you get hundreds of economically impotent micro-states fighting it out for land and resources. Do you make the states big enough to balance out the ethnic groups and absorb the nonviable states like Chad? Then you get Africa's OTL problems, but bigger, and with zero infrastructure to hold them together.
How about a slower decolonization? I get what some of you are saying, that if only it was taken slower, things could've been better. But that is impossible. One: most of the pro-independence Africans would not have consented to a "slow" approach; they wanted it asap, which is reasonable. Two: I
highly doubt the European countries would seriously have spent the time and money to ensure stable, well-off regimes were in place. More likely they'd put "big men" in who would follow orders from the metropole.
Now, I fully believe that PoD's can be made to butterfly away this or that war. But I do not believe that Africa post 1900 could have been made
substantially (thus not just cosmetically) better without changing the European conquest to something other than, well, conquest. There's no way, I think, to have the calamity that was colonization end in a good way unless you seriously change Europe's goals and policies towards Africa from the beginning, and I can't see a PoD for that post-1900.
Africa isn't even unusual in its responses to decolonization. It took Europe like what, 1200+ years to achieve serious stability after the fall of Rome? It took Latin America from independence until the end of the Cold War to achieve some sort of lasting, not dictator-induced peace. To be optimistic, relative to the absolute shellacking Africa got it's recovering fairly quickly.
tl;dr: I'm a wet-blanket who doesn't think any PoD is viable for this situation.