Being "nice guys" loses again.
The USA did not follow the admonitions of Machiavelli. "It is far better to kill than to injure." The USA should have rounded up the ENTIRE Ba'athist Party IMMEDIATELY after the conquest and shot the lot of them, promptly, without trial, or at least put them into the dungeons. This would have put out the word that we were not to be truckled with. Instead, we wanted to forgive. We just put out arrest notices for the bigwigs and left the smaller fry to re-organize. Mercy is NOT respected in the Arab World, only strength.