I am one of the few people here that still stands by the decision to invade Iraq, I think it was the correct choice but implemented horribly.
Since 2003, the philosophical goals of the war and tactical decisions, from President to President, from General to General has really been the reason for its failures. We can debate that in much more detail if anyone would like.
But the fact also remains that the lasse faire approach that was seen by this country from 1993-2001 under Clinton (where we had very little involvment in the Middle East at all) did not work either. The philophy of "letting the arabs fight among themselves" has not worked because it is proven, based on the terrorist attacks from 1993-2001 up to events of 9-11, that when given time and relative peace, they will plan and execute terrorist attacks on western targets.
One of my main reasons to support the invasion of Iraq and keep LOTS of boots on the ground in the Middle East has long been the concept of giving terrorist extremists a MILITARY target rather than a CIVILIAN target. Yes, troops will die during this era, although hopefully it is few and far between as we learn and understand how to defend ourselves. But by giving extremists in the region closer targets, they will be much less likely (other than rogue lone wolves) to plan massive attacks on western culture.
I just don't support "leaving". Maybe ever. If we can keep 30,000 troops in South Korea and 40,000 in Germany, we can keep 25,000 troops at high-tech, high-end, permanent military bases in Iraq. Unfortunately, we allowed Iraq's government to turn into a proxy Sharia Law, Shiite state supported and propped up by Iran. It's not at the level of Syria and Assad, but it's not as far away from that as it should be. So maybe we can't stay there anymore, despite it's ideal location.
We should have spent the trillions of dollars creating a true representative, secular government in Iraq. Moved most of our assets out of Turkey and Saudi Arabia (who are not good enough governments to be "true allies") and created a truly central power in Iraq that would get all the economic benefits of being the greatest ally in the region to Western economies (U.S. and European Union). This would have taken decades and trillions of dollars, but could have been achievable with the right leadership and foresight.
It's just too bad we debate leaving and are on the brink of resetting the whole region back to 1990 with the possibility of reliving everything that happened in the last 30 years all...over... again (including the likelyhood of a major catastrophic terrorist attack on western soil claiming thousands of lives).