OK, I have read this thread through and here are my opinions.
None of the nations above should be out of the game. However, if one had to go I would still choose Mali. Because not many people no that much about them, therefore they don't want to play as them. You can argue all you want that Mali represents Africa, but it represents the Islamic community more. Also, don't forget about Egypt, Egypt is in Africa and you could just as effectively argue that Egypt represents Africa as well as Mali. The truth is, neither represent Africa as we all think Africa as. Mali should be out, and Zulu back in. This is of course just my opinion.
Now my second canidate would be Aztecs. We already have a North American nation represented (Aztecs were located in central mexico which is north america, not central america). Plus, the Aztecs didn't really influence past history. They were a primitive people who conquered nearby tribes and their only claim to fame was being conquered by the Spanish conquistadors.
You will notice I don't think Incas should be out, because they are the only nation that represents South Smerica. Also, they were more culturally advanced and technologically advanced that the Aztecs. They were especially advanced in the medical field. I feel they should stay.
My third canidate would be Spain. Spain, because I think the only real world power they possesed was during the Age of Discovery when they colonized the New World and the Phillipines. After the age of discovery and the Spanish American war in which America got Cuba, Puerto Rico, and the Phillipines in there victory, it kind of feels like the spanish power just disintegrated. No offense to you Jonathon. (I noticed you were from Barcelona)
Now, I have to add my two cents dealing with Mongolia and America.
First Mongolia. Although Mongolia was a culturally lacking nation, for the 250 years it existed it conquered almost all of Europe and Asia. It had the largest nation ever in world history. Because of Mongolia, early russians were completely stunted in growth. The mongolians marched from city to city, civ to civ, conquering and killing. They affected world history immensely even though it was in a negative way. They left no one alive in cities they conquered except men who could be recruited in their army. Because of them, cities were annihilated. No one can say they didn't affect world history. They came the closest to conquering the world than any other civ (although they weren't really "civilized") ever in world history.
OK, here comes the long argument. America has had a huge impact on world history, regardless of what you think of it's current government policy. You can't uninclude them in the game because they are the youngest nation. First off, people who argue it ruins gameplay when American warriors are running around in 4000 B.C. I have this to say to you. This is just a game! I realize many people like to have realistic and historic aspects when they are playing (I do sometimes too) but is being one leader for 6000 years realistic. And if you argue that America is too young and didn't exist in the world in 4000 B.C. None of the other civs did either except the Sumerians (who aren't in the game) and Egypt. If you argue that America can't be in the game because they didn't exist in 4000 B.C. then you have to argue that the Aztecs or Incas can't be in the game past 1600's or else your argument doesn't make sense. Now, for anyone saying that America shouldn't be in the game because it is to simaliar to England I have this to say to you. Yes, the first of us came to America from England. But also from France and Spain. Once we gained our independence the US became the melting pot of the world. French, British, Spanish, Germans, Italians, Chinese, Japanese, Dutch, and Irish all immagrated to the U.S. and still are today. You can't say that our sole backround is from England. Nor can you say that America and England belong to the same civilization. If you say that then what you are arguing is that, America, Canada, England, France, Portugal, Spain, Holland, Germany, just to name a few, should all be combined into one nation called "Western Civilization." Then you would also have to combine China and Japan and other nations that are simaliarly civilized. This doesn't make any sense. America is the world's leading super power, the world's only current superpower. It has influenced and still influences the world economically, industrially, politically, technologically, and militaristically. I wish I could continue on with examples and excetras but I don't know how better to explain by point of view. Either way, my opinion is, that the idea of getting rid of America because of SOME (not all) of the reasons people have posted in this thread is absolutely absurd and in some cases ridiculous.
P.S. I just thought of something. We are all arguing about a game including America in it when the game was created in America.