By the end of 2011 Obama pulled all our troops out of Iraq because they would not renew our Status of Forces Agreement, which gives our troops immunity on the field of battle. The one that was put in place by Bush expired and they would not sign a new one. Obama had no choice but to pull out.
When we started placing forces back in 2014, we went in because they asked us. They renewed the (SOFA).
If they pull it again, Trump will be forced to pull out unless he wants to be an invading force.
And McCain made it clear he wasn't putting a time table on leaving.You are smart enough to know Iraq cant make The US leave if The US president doesn't want to leave