If the US withdrew completely, and disengaged completely from that part of the world (assuming we could meet our oil/energy needs without Gulf oil), what would happen? I mean, apart from Lindsay Graham and John McCain, and the Israel lobby having strokes, of course.
Either a Caliphate is established, which would not please Turkey, Iran, or Israel, or one or more state actors would step in and intervene, and stick to tar baby. In either event, the EU has FAR more at stake than do we. Let them deal with it, or not, as they choose.