I'd suggest rethinking the term "failure." In occupied Europe, the Nazis were extremely successful. They imposed client governments which ran the countries including the security forces, with Germany always in the background, but not much involved. The partisans were very courageous, but would have been wiped out without massive foreign support. Russia was even more successful in Eastern Europe. Plenty of other cases. The issue is not success or failure in such cases. Or Iraq.
...No serious person pays the slightest attention to stated objectives of great power(s). They carry precisely zero information, because they are entirely predictable: nobility of purpose. That’s true of even the worst monsters.
In this case, there is every reason to accept the view of the overwhelming majority of Iraqis expressed in US-run polls: that the goals are to control Iraq’s resources and to use Iraq as a base for extending US control over the world's energy resources. It's true that we are sternly instructed to believe that the US would have "liberated" Iraq even if it was producing pickles and lettuce. It takes North Korean-style subordination to authority to accept the Party Line in this case.
There's very good reason to believe that the US will continue, as until now, to do anything it can to prevent realization of the "stated objectives": democracy and sovereignty. It's sufficient to consider what the policies of a sovereign democratic Iraq would be: an utter nightmare for Washington.
... The Kurds would doubtless prefer for the US to stay, as long as the US doesn't once again betray them, as it has done, repeatedly, in the past. The Sunnis, about as numerous as the Kurds, doubtless want the US out. As for the Shiites, it's not so simple. The Sadrists have called for withdrawal. The last poll I know of was on the eve of the election: about 70% of Shiites favored US withdrawal immediately or right after the January elections. The National Sovereignty Commission of the Parliament recently issued a report calling for a timetable for withdrawal of the "occupation forces." The main Shiite Party in the South, SCIRI, just demanded that the British troops there stay in their barracks. According to Steven Kull, one of the most respected polling experts in the country, the International Republican Institute, which had been taking regular polls, stopped reporting them after the elections because of the results they were finding.
It's correct that an occupying army has no rights, only responsibilities, including the responsibility to pay massive reparations and to withdraw unless there is powerful evidence that the population wants them to stay. I don’t see evidence of that. And the decision should be made by the victims. We have little to say about it, whatever our subjective judgments, as a matter of principle.