By your logic we should support Assad. Actually, that would be a far easier way to end the civil war than by resorting to any other outcome.
Still, though, regardless of what you think of the US invasion, at the time when Obama foolishly withdrew US troops and turned Iraq over to the completely incompetent and utterly sectarian Maliki, there was no ISIS in Iraq. While the invasion destabilized Iraq, the troop withdrawal destabilized the fragile peace we had managed to piece together.
ἡ δὲ κἀκ τριῶν τρυπημάτων ἐργαζομένη ἐνεκάλει τῇ φύσει, δυσφορουμένη, ὅτι δὴ μὴ καὶ τοὺς τιτθοὺς αὐτῇ εὐρύτερον ἢ νῦν εἰσι τρυπώη, ὅπως καὶ ἄλλην ἐνταῦθα μίξιν ἐπιτεχνᾶσθαι δυνατὴ εἴη. – Procopius
Ummaka qinnassa nīk!
*MySmiley*