It is not NEARLY that simple, and you know it. Plenty of Republicans are unhappy with the way he did this, as well.
For the record, my gripe is not that he withdrew troops. I am for that in the big picture, too. But doing it on a whim, in such a manner as to capture everyone by surprise so that people suddenly have to leave as war refugees, leaving the Kurds unprepared to defend themselves from an invasion, creating an opportuniy for ISIS fighters to be released or easily escape and merge into the background, and not consulting with anyone at all beforehand, was just stupid. Plenty of Republicans feel the same way.