What's a country to do?

One question, accepting that the US has seriously blundered in their handling of Iraq, what should the US do? They have found themselves in a genuine Catch 22 situation. If they leave Iraq.....just get up and go....most "experts" and "analysts" believe that there would be a civil war within Iraq between rival Islamic factions. What can the US do?

Should the US just "get up and go"? Should the US simply leave and allow an almost certain civil war to tear the country apart? Should the US simply leave and allow one Islamic faction to dominate the other? Is there a genuine possibility that if the US left Iraq, then the varying Islamic factions will come together, rebuild a decent Islamic society based on genuine Islamic beliefs and laws?

I know that these questions have been asked by other others and on other posts but the answers have never been concise and clear. Sure there are a few questions being asked her but what are the answers