Apart from the rather dubious premise for the invasion of Iraq in the first place the question remains are the people of Iraq, on balance, better off now than they were before the occupation of their country? The infrastructure has been destroyed and thousands have been killed and wounded. That people are still questioning what the future will hold is, in itself, an admission of failure. The cost of that war to the American treasury is estimated in the trillions of dollars not to mention troop deaths and casualties. While the USA was satisfying George W. Bush's desire to kill and capture Saddam Hussien the effort in Afghanistan floundered and opponents there regrouped.
As it currently stands Iran has gained influence at the expense of the west both in Iraq and to a lesser extent in Afghanistan. If the American goal was to bring peace and stability to the region they have failed. With all the military might available there is still no end in sight.
The USA should take heed with what happened to the British and the Russians when they attempted to occupy countries in that region.