If Sunnis, Kurds and Shiites were to successfully pull together, would the US pull out if asked?

Yes, I do think we'd pull out. However, if you do a little homework and research the histories of those people, you'll see that they've distrusted one another for centuries. I think the real mistake the Bush Administration made was thinking for one moment that they could actually get those three groups to form a coalition government. They can't. It's not like republicans and democrats. These are people who have hated each other for centuries. It's not going to work. The US policy in Iraq has been doomed from the moment we left the power vacuum by capturing Saddam Hussein. Don't get me wrong, he was a terrible ruler who did some awful things, but they needed to have a new leader ready to take over, and that hasn't happened.