Africa might be 3 times bigger than Europe, Europe was twice more populated. It was between 1995 and 2000 that Africa's population surpassed Europe's population. Before 1950, Europe was 6 times more dense than Africa most time in history. Europe might be overepresented (15* European civilizations vs 6.5** African civilizations), but it is kind of the consequence of history. That, and also the fact that European have better preserved his recorded history, so the Civilization team have more tools to create something. Plus: the Civilization team kind of stopped to represent civilizations that appeared or culminated, or history that occurs after 1950 (Stalin and Mao say hello). Sub-saharian countries kind of boomed after 1950, and I think they are writing history right now.
I say that, but I would love to see more civilizations in Africa. The Civilization franchise made me learn about history, and now surprises me with unexpected but fascinating civilizations (Cree, Mapuche, Scythia, Nubia...) or leaders (Catherine de Medici, Eleonor of Aquitaine (well: I knew about her, but they make me realise how impactful she was), Tamar, Simon Bolivar, Lady Six Sky, Jadwiga...).
* : the Netherlands, England, France, Georgia, Germany, Greece, Hungary, Norway, Ottoman/Turkey, Poland, Roman/Italy, Russia, Scotland, Spain and Sweden.
I am not includind Macedonia, because it is just warmonger Greece with better suiting abilities. The old kingdom of Macedonia do not exist anymore in today time, and North Macedonia isn't the continuation of it: it just pop out as "not east-Bulgaria" during Yugoslavia period. I will stop here, because I am becoming contraversial (this post is already too much contraversial).
** : Egypt, Ethiopia, Kongo, Mali, Nubia, and the Zulu people. I am including Phoenicia for 0.5 point, because it is kind of mixed bag with Carthage.
The "race" debate. This is a never ending subject. Mostly because nobody have the same signification of what a "race" is. The view on the subject may differ largely between civilization. Let's take France. You would think the French people would see the matter roughly the same way than most people from Anglo-Saxon countries see it? After all, you just have to cross the English Channel*, so how can it differs? Well, it differs immensely.
* : I may be wrong by assuming UK and USA share roughly the same view on the subject, even if I am pretty sure UK is probably in between.
First, all ethnic subject is kind of taboo in France. Even the word "race" is forbidden word, as you get categorized as "nazi" just by using the word. Yeah, it is that taboo. Using the word "noir" (french for black) is kind of tricky, because it kind of feel like the word "******" without being the n word (french for "******" is "nègre"), so people rather use "renoi" (yes, verlan or the way of inverting syllables of a word, because french wasn't hard enough) or "black" instead (yeah: the litteral english word). Using "african" is starting to get taboo, so now you better use the nationality instead. Random fact: ethnic statistics is forbidden in France, I guess now you are realising how taboo the subject is in France*.
* : I do believe religion play a role on the perception. And the majority of French people neither believe in gods nor follow a religion. The majority are registered catholics because they are baptized by tradition before they were 3 (no consent). The fact that France is secular state kind of played a role. I must admit admit I found funny when I see in TV-show that people are supposed to swear on bible in court in USA. Are you going to file for blasphemy if they lied? Or pledge of allegiance. All the things like this seem crazy to me.
Even how you view people ethnicity can differ greatly. Let's take the "Obama" test: most American will say he's black, and most French will say he's kind mixed. Maybe because they see overseas french people as creole, kind of black people but mixed (lighter skin), and Obama is significantly lighter than most creole people. Other example, hearing American people speaking so freely about "race" and saying thing like "white can't dance" or "black can't swim" (even for the joke) is something really really REALLY uncomfortable to hear for most French people.
From this point of view, there is no relevant black-american civilizations because there is no black-american nation at all. Living next to Suriname and knowing a little about Guyana, I can see there is no majority ethnic group in both countries. Even if they are the two mainland countries in South/Latin America with most black people, the black people themselves are not the most numerous: the East Indians are.
Overall, people there in South America do not really care about there lineage (in a sense: trying to preserve a "purity", even if they are proud of their mixed heritages), and South America countries are mostly populated by people with mixed origin.
The only exception might be the Carribean, but even the Domican (share the same island with Haiti) saw themselves as mixed than really black people. But they are seen black with the American tinted lens, because they see the "race" subject in a different view.
But the point is not: should we have a black-american civilization? Because the question is nonsensical: there not really is a black-american civilization to begin with (well seen by a french tinted lens), and adding a civilization just to fill a quotat seems to me the worse reason ever.
For me, the real question should be : "Is there a civilization/country born from slavery that it is interesting or worth representing?" And the answer, for me, is obviously yes. But which one? Haiti was the location of greatest and iconic slave rebellion resulting in a success. It is too bad the country is currently poor and have difficulties to rise. I am afraid it feel as Gran Colombia: a one-time history moment. And I don't want people smashing the dislike button on Haiti (I don't want my heart broken) because they don't want to open their minds about that one-time history moment, and just see on how is the country now.