putting the blame on the withdrawal is pretty much saying that the better option was a permanent bloody occupation of Iraq, which most rational minds know was unsustainable.
By the end of 2009 there was very limited US involvement in Iraq and there was no "permanent bloody occupation". The US transition from the Awakening to Iraqi sovereignty was well in motion with the US functioning as an advisory and stabilizing influence that gave hope to Sunni and Shiite reconciliation and sharing of power. The complete withdrawal of forces and diplomatic involvement empowered the militant Shiites emboldened by Iran that led to the melt down that followed. It was the change in policy towards disengagement in Iraq and the rest of the Middle East in the Arab Spring that followed that empowered the Jihadis which led to the Islamic Caliphate know as ISIS.
In short, Zimme's assertion of the US invasion itself leading directly to ISIS is contradicted by what most every credible source describes. It was one step among many in an evolving chain of events but to then draw a causal relationship in spite of that evidence seems implausible.
https://en.wikipedia.org/wiki/United_States_Forces_%E2%80%93_Iraq"During 2008 and 2009, all non-U.S. foreign forces withdrew from Iraq. Withdrawal of all non-U.S. forces was complete by 31 July 2009. As of 1 January 2009, the Iraqi government became fully responsible, through its security ministries, for maintaining and providing security and rule of law for its populace. Furthermore, as of 28 June 2009, no foreign forces were stationed within any of Iraq's major cities. The United States decided after negotiations to cease combat operations, that is, patrolling, serving arrest warrants, route clearance, etc., within Iraq by 1 September 2010, and transition to a pure advise, train and assist role. The changing mission entailed major troop reductions; from 115,000 on 15 December 2009, to 50,000 by 1 September 2010, and to zero by 31 December 2011."
