I'm more surprised that the Incans and Aztecs don't rank into the third tier, conquered or not, they DID have a big influence over the time period due to the nature of what they were, how they were conquered, etc. Same could be said for the Iroquois and Cherokee, if only for flavor in North America.
....DLC? Paradox, take my money.
....DLC? Paradox, take my money.