And the problem is, the rest of the world can't leave the Middle East alone, because
1.) There are a large number of suffering, innocent people who want nothing more than to get out of their present situation, and
2.) Instability there could affect the rest of the world; we know extremists and other West-hating people are perfectly capable of demolishing everyone else.
1.) We don't have a problem with suffering. Witness Africa through the ages. Also, most countries in the coalition, along with the US itself, would be ecstatic to merely provide civil and medical assistance to the in-country refugees, if it meant they could withdraw their troops. And face it, the continued military presence isn't doing any good for the situation of the civilians and it sure as hell isn't enforcing peace.
2.) There has been instability in the Middle East as long as I've been alive, and a few thousand years before that. As long as the economical targets stay stable, how would the rest of the world be affected?
The real problem is that the rest of the world
won't leave the Middle East alone. What comprise the source and start of the majority of the problems and unrest in the Middle East today? Western meddling.