And how has Ethiopia affected history apart from being on the news for it's famines and civil wars?
Canada at least fought in two world wars.
This is the modern "Ethiopia"...take a look at the Ancient country, which is also known by the name of "Abyssinia" or something along those lines. They were prized mercenaries for Carthage, invaded Egypt (according to Herodotus, at least), and were otherwise significant players in North Africa.
The Celts were historically a major civilization, spanning most of Europe before the Romans conquered large portions of their territory. However, they are not a true "empire" because they didn't have a centralized administration, much like the ancient Greek poleis. Even during Alexander's time, the League of Corinth (an organization of most Greek poleis, not including Sparta) would rebel against the Macedonians (happened twice, if I recall). However, for some reason, nobody questions the Greeks but will pile on the Celts.
The Zulu were rather quick in conquering a large swath of Africa...then they ran into the Europeans, and it turns out that little technological advantage of firearms really came back to hurt them. I personally think there are a handful of "more deserving" African nations than the Zulu, but I won't detract from the conversation here.
I would also question the "Native American Empire", which is one of the most horribly named stereotypical civilizations the Firaxians have added. They could have at least called them the Sioux or something specific, instead of a general term applied to all the native American civilizations including the Aztecs, Inca, and Maya, but instead shot for stereotyping native Americans with Sitting Bull, totem poles, bows and arrows, and other "Plains Indian" stuff. Overall a quite bad choice...I'm still wondering where all those well-defended walled cities with incredible archers the Native Americans built are...
I would argue against Canada and Australia, and for the simple reason they decided to stay within the British Empire for centuries instead of forcibly separating themselves. I'm not saying the choice to stay with Britain is any more or less correct than the US approach to rebel, but the US intentionally struck a much different chord with Britain in 1776, and distinguished itself as entirely separate (and therefore more worthy of "Civilization" status). If I'm not mistaken, the Queen of England is still the "official" head of state of both Canada and Australia.
@dutchking: When you said that a particular Mod simply spammed a number of insignificant modern states...I'm thinking yours is looking awfully similar. If I was modding this game, I would only modify 2 or 3 existing civilizations and then add a handful more, not the 10+ you have in this mod.