Iraq...let it transition to a three state 'stability'

The rise of ISIS in Iraq brings the country closer to a Shi'ite/Sunni War. I don't have sympathy for either side but I do not wish for the country to slide into a war. Should the US intervene? I don't believe that it is in American interests to do so. While it is clear that Obama's premature evacuation of American forces, folllowing the gains of the 2007 surge, may have exasperated the condition it is in everyone's interest to allow local parties to sort this out themselves. Iran will do their best to support Shi'ite interests and will most likely supply enough ground support to nullify the Sunni Jihadists (as they did in Syria). The end result may be the division of Iraq into three sectors: Kurdish (which is already de facto), Sunni and Shi'ite which seems to be the most natural breakup of this region anyway.