Not much reason for the US to jump in - we may have screwed up in the past, but as for what's going now, the Iraqis need to work it out.
The tricky issue is when "working it out" means massive slaughter of one sect by another, intentionally triggering the wanted counter-slaughter. It no longer looks like the Shiite-dominated government will fall, but if it did seem under threat, I could theoretically imagine airstrikes on troop movements that only keep ISIL out of Shiite cities (if airstrikes would work, which is doubtful). Some real changes in the government's behavior could be reason to support it, but otherwise we should stay out.
ISIL seems momentarily popular in their part of Iraq. Fine, let's see how long that lasts. I doubt they'll have ability or energy to attack foreign countries given what the civil war they're dealing with now.
While consistency might not be the most important thing in the world, I think I'm taking a consistent position on this as with saying the West shouldn't conduct airstrikes in parts of Libya that supported Gaddhafi and that we shouldn't have a troop surge in Afghanistan in the parts that rejected Karzai.
Finally, I don't think this will be seen as a political problem for Obama - the Republicans who claim otherwise will be asked if they learned anything at all from the Iraq War.
