I agree with God
Americans have the best traits for the larger maps. None of the UUs have a major impact on the game, they're just nice to have and give you a good feeling about your favorite civ.
The civs are remarkably balanced in traits and UUs combined. I wouldn't say any should be called the worst, although some are better on certain maps (large or small) and some would better fit a person's style than others.
As for that Impi, it beats the well regarded Jaguar Warrior in every aspect except price, and the price ain't bad. In the first era the Impi is a great defensive unit on larger maps because it can move fast to reinforce threatened cities, where a regular foot unit couldn't make it. Against restless (or raging) barbarians the Impi is great. For example, in my latest game a massive barbarian uprising spewed about 80 barbarian horsemen into my territory in one turn. About 40 of them attacked one frontier town in the next three turns. Another 16 attacked another town on the other side of my empire. In this kind of situation you want to move defensive units very fast, and the Impi would be my first choice until Knights come along.

Americans have the best traits for the larger maps. None of the UUs have a major impact on the game, they're just nice to have and give you a good feeling about your favorite civ.
The civs are remarkably balanced in traits and UUs combined. I wouldn't say any should be called the worst, although some are better on certain maps (large or small) and some would better fit a person's style than others.
As for that Impi, it beats the well regarded Jaguar Warrior in every aspect except price, and the price ain't bad. In the first era the Impi is a great defensive unit on larger maps because it can move fast to reinforce threatened cities, where a regular foot unit couldn't make it. Against restless (or raging) barbarians the Impi is great. For example, in my latest game a massive barbarian uprising spewed about 80 barbarian horsemen into my territory in one turn. About 40 of them attacked one frontier town in the next three turns. Another 16 attacked another town on the other side of my empire. In this kind of situation you want to move defensive units very fast, and the Impi would be my first choice until Knights come along.