You shouldn't let your politics get in the way of your view of this war. A great number of a mistakes were made and many of the objectives laid out when we first went to war were never accomplished. They were not accomplished, NOT because our troops lacked the ability or strength to achieve them, but because poor planning or poor intelligence made the task impossible before it was even begun. On top of that it will take years if not decades to judge the full effect of the Iraq War, right now their government is pretty shaky and it falling apart would not be a victory for the United States.
We owe it to the troops who died, those who were killed or wounded, to recognize the mistakes that were made, the failures in intelligence and planning that led to some objectives not being complete. I know you'll probably look at this like Vietnam and declare that once we leave, what happens there stops counting and has nothing to do with us. I don't know how but somehow you deny that our actions have effects the day after we leave, and I tell if this government falls apart part of the blame will belong with the United States. After all, we are the ones to help create it and we should get some credit if it succeeds and blame if it does not. Don't make use the same argument you had for Vietnam, that when we left South Vietnam was a Democracy, never mind they never had an election and were overrun in a few short years, it was "ok" when we left, thats all that counts, that means we won!!
Its about more than winning and losing, and those terms are so hard to define in these kinds of wars. No, admitting mistakes and looking where we error-ed, is important and we OWE it to the troops to ensure we don't place them in impossible situations again, or situations were their sacrifices are ultimately a waste because our information or planning wasn't up to standard and someone was killed over it.