Good story at the WSJ:
With the U.S. gone from Iraq, emboldened jihadi forces shift to Afghanistan and turn it again into a bastion of Terror International. Syria reclaims Lebanon, which it has always labeled as a part of "Great Syria." Hezbollah and Hamas, both funded and equipped by Tehran, resume their war against Israel. Russia, extruded from the Middle East by adroit Kissingerian diplomacy in the 1970s, rebuilds its anti-Western alliances. In Iraq, the war escalates, unleashing even more torrents of refugees and provoking outside intervention, if not partition.That's just a taste of what would happen, of course.