Inca in the hands of human.
Monty in the hands of the AI.
edit: just wanted to comment about america. I do play them frequently (though probably less than 10% of my games). It's not blind patriotism. Or maybe it is. I don't understand why the left thinks patriotism is that bad. Is it wrong to love my country? I guess I'm prone to loyalty. I am partial to my country, my state, my city, my company I work for, and my family. Not necessarily in that order. As you can see they are in increasing scales. All of them are just extensions of my family. So if you have any feelings whatosever for you family, why not your country? I know this is off topic, but it's something that's been bothering me alot. Patriotism is not bad.
that said, america in game is ok. The traits are ok for a builder civ. The uu is largely useless, but you can win this game without uu's. So that's why I don't mind playing the U.S. I don't need a uu to win. Malls come too late as well, but I usually build them anyways.
And I feel all the other american civ uu's are overrated. I play on huge maps, and find the Inca's uu almost completely worthless. The only reason I rank them so high is the financial trait which is OP. Dog soldiers and the Mayans uu are worthless as well. I don't like defensive uu's. If the unit can't help me take a city, what good is it?