Should we leave Iraq alone?

Now, there is a civil war. So what? There are civil wars all over the world. Why do we have to play world police there? PLEASE, do not say, "we're there to fight terrorism", because there are larger and more widespread terrorist cells in other countries. So, if we are to fight terrorism, why not focus on someplace else? We've spent a gross amount of money on this war that could have been spent bettering our country and many lives have been lost. PLEASE, also do not say something like "we dont want another 911, so let’s fight them there instead of here", because there is no guarantee that we're any safer from terrorist attacks here if our troops are in Iraq. It would seem that we'd be safer if our soldiers were here protecting our borders; so, why don’t we just bring our troops home? I mean - Why do we care how stable their govt. is? Why not invest the money we're spending over there on our own economy, defense, education, roads, crime, etc?