To me its not about wanting to play as terrorist. It's not wanting to play as american soldier. I see it as another attempt to market the american way of life to the world. Frigging yanks can't brainwash me!
You're not exactly the intended audience
Its a recruitment tool, with a side order of training. join the army, be the good guys, etc...
There was an article a while back when it was released where they asked the developers why they did it that way. I'll look for the link. Suffice it to say, its pure propoganda. They want you (and by you, I think they mean 18-25 US citizen) to feel liked you are on the "good guys" side, and get you used to helping out guys with American flags on their shoulders.
Somewhere along the way, the accidentally made a decent game that people like playing.