Many otherwise-clever Americans have been led to believe that the USA should "stay the course" in Iraq, because a U.S. military withdrawal would leave a dangerous and tragic vacuum.
But there are nearly 200 other nations in the world; those concerned can assist if necessary, probably in cooperation with Iraq's nearby neighbors.
Various others people of the world (also) have vested interests in Iraq. Most Americans do not.
Many Iraqi and Kurdish people detest continued American interference. Most Americans would be better served by US federal spending at home, not in far-off Iraq. Persistent violence in Iraq is killing & brutalizing far too many people. The USA never should have taken the unilateral decision to invade; the key reasons given at the time have now been accepted as erroneous.
Let's imagine a North American scenario -- the USA and Mexico are presently arguing about border security: what if a belligerent European, African or Asian nation inserted troops?
No way José.
Bring US troops home from Iraq.