Most of the 9/11 hijackers were Saudis — our allies. The Middle East isn't strategic to America's interests anymore and the less we're involved there the better off we are.
We failed in Lebanon. We failed in Iraq. We're failing in Afghanistan. We failed in Libya. No matter how cold and distant it seems, there's simply no reason for America to expend vast resources on an impossible task urged on us by a bunch of putative allies who are only interested in using us as a mercenary army. We should protect ourselves against the export of terrorism from the region—which might sometimes require a military solution—but that's about it. It's far past time to ratchet down our engagement in the region and let other countries take the lead if they really want to.