The trendline is going to be, as the months go by, Sunnis increasingly wanting the Americans to stay as protection against Shi'a revanchism. In the meantime, it is true, the Shi'a will get increasingly agitated vis-a-vis the Americans for holding them back from revenge attacks in the aftermath of events like the recent destruction of the shrine. But haven't we an obligation now, in one of those complex ironies that emerge from the fog of war, to protect moderate Sunnis from the wrath of Shi'a provoked by al-Qaeda and FREs [?] (indeed some Sunni areas are becoming more fearful of Shi'a paramilitaries like the Wolf Brigades than their ostensible American foes)?
Short answer: Yes. Though, I think this situation is more a test of the Iraqi police and divisions.
Oh yes, it is ironic and it must be quite humiliating for the Iraqi Sunnis to ask for help from the imperial, oil-stealing Americans.