I think we also failed to anticipate the breakdown in civil order. Our failure to immediately stop the looting and crime was resented by many Iraqis. Where we have now restored order, where Iraqis can work and go about their lives in relative safety, there is gratitude for what we've accomplished.
Even if it had anticipated it with absolute certainty in Iraq, how would the outcome have been any different? We can't control the eruption of a riot in any given US city after a football game if a mob is so inclined.