Saddam was obviously bad for Iraq, but he had a solution for sectarian chaos (a brutal one, but a solution nonetheless). America opened up a can of worms by removing him, doesn't take the brutal route he did, but doesn't even understand the sects enough to redirect them in other ways. Furthermore, ruins it's good name by recruiting every shit-for-brains "at risk" delinquent they could get their hands on - not to mention mercenary groups. Some of these guys killed civilians for sport. The result: Everyone hates us (while still hating each other too). After enough times, even random, collateral damage to civilians gets seen as purposeful and antagonistic. And the extremists used that to their advantage, getting more and more people to hate the US. They're the ones on the ground, in the villages, making contact, while we don't know shit about how to make lasting friendships with the typical people there.
This whole situation might have had good intentions, but that doesn't mean much. I hate to blame this on "F" types specifically (could be latent F impulses in strong T types), but it boils down to black and white idealists and moralizers who think merely doing "the right thing" is all you need to accomplish a mission. Everything is seen through the lens of ethics. Would you screw in a light bulb with ethical logic? No. Yet, some people want to employ that kind of thought to war, of all things. That only works in fairy tales. War is sometimes necessary, but people would do well to not get stirred up about the "right thing" to do and think about logistics for a change.