What prevents the USA and the British from entering a full blown war in Iraq (again) against ISIS?

When Captain Philips was held hostage by Somali Pirates eventually the U.S. sent snipers to handle the situation. My question is, is there anything preventing a full scale assault against ISIS or is the U.S. having fun playing with it’s drones in Iraq?

Also, how hard would be to track down the HQ of ISIS? Surely satellites have tracking capabilities of enemy strongholds in 2014? Or have I been far too spoiled in the video game realm?