Tonight in the Democratic Party Presidential debate, they were all in agreement that the Iraq War was the worst foreign policy mistake in American History.
In 2009, when GWB left the White House the nation of Iraq was stable, Al Qaeda in Iraq if not totally defeated was badly beaten and on their way to defeat, and the nation of Iraq was heading in the right direction.
What happened? Obama failed to negotiate a Status Of Forces agreement allowing US troops to stay in country to insure the progress would continue in the right direction. The US troops in country were the one honest broker that would be able to see that the Shia, Sunni, and Kurds all got along.
Obama and Clinton then neglected Iraq and dropped the ball during the Arab Spring allowing Iran to extend it's influence in Iraq leading to the neglect of the Sunni and Kurdish area's of the country, which in time led to the rise of ISIS and a new civil war in Iraq starting in 2013.
If Iraq War is the worst foreign policy mistake in American History, it's because of failure, neglect, and negligence directly attributable to the foreign policy of Obama and the Democratic Party.