Actually it would be easier for the Iraqi forces to retake the towns that the ISIS militants have occupied after the US bombs the ISIS equipment, weapons and stronghold.
However, it's another scenario in Syria itself. At this time, I would assume Assad's forces are more likely to finish the job after the US bombs the ISIS stronghold, equipment and weapons. If they don't, the so-called friendly militants would take control and Assad's power will more likely be degraded.
