I think the Americans are Commercial and Militaristic.
I can see how you get to that view, but I have a different take on that. Sure, the USA is the world's number 1 military power now, and they're not afraid to use that power either, but still their society is not really much based upon their military organisation. While if you look at Sparta or Rome or the Mongols in their day, then you see that the whole civilization was much more structured around the military.
America always seems to have a commercial agenda. I would call them just commercial, and not much else. They're expansionist in the game, but why? They've only actively engaged themselves with the world around them for about 50 years just now, before that they were quite happy just being independant America, probably still looking for their own identity. Not surprisingly; the whole country as an independant nation only exists for just over 200 years, that's nothing in world history terms. Should they be in civ, you could ask.
And Capnvonbaron, you're of course right to say that the modern western European nations are not exactly the inventors of many basic agricultural techniques as they borrowed lots. But now they're forerunners, and have become exporters of knowledge, breeds, orginisational techniques and engineers. The Dutch are Agricultural in the game, well, you can hardly go anywhere in the world without seeing those Friesian-Holsteiner cows, they do a lot of groundbreaking engineering with their crop growing and manipulating - not always good - and their engineers are hired everywhere for drainage projects. Although it's not a very agricultural society. More commercial, like you say. It seems very hard to get around the commercial bit these days.
But I agree with Turner; this is a game and history is an inspiration for it, but it doesn't need to be a harnass. I'm also more concerned about agricultural being a bit too strong than which civ should have it and which not.