I think wealth plays a large part. If I'm in poverty in the US I'm still in relatively good shape. If I'm in poverty in the middle east I'm really in poverty, add a lower education level, constant warfare and you have a recipe for disaster.
I don't think it's anything inherent to Americans but is a product of our wealth and stability, something which the middle east hasn't had. (Something I'd also point out makes it fertile ground for Islamic extremism to take root)
Americans have (or maybe had) a sense of individuality, the byproduct of which is respecting the freedom of others. And it used to be that we weren't all that offended by every little thing. Back in the day, if you call a guy an *******, if he gets offended, maybe he just punches you in the nose. I think the America we're becoming will devolve into an America that will see more people willing to harm other people for no good reason.