It makes all the sense in the world. Anyone who thought the U.S. would be welcomed by these people with open arms was terribly naive. The attitude of most Iraqis can probably be summed up as follows:
"Thanks for getting rid of Saddam Hussein. Now get the f#&* out of here."
I would ask that some stop, take a deep breath, and realize that we only mostly see every negative thing possible, and none of the positives that are occurring.