US and the creation of ISIS

Western correspondents in Beirut have been reproducing Syrian rebel accusations: that the Syrian regime had created ISIS and their evidence is their claim that the Syrian regime never fights ISIS. But the US clearly has been avoiding fighting Nusrah Front (and even created an artificial silly distinction between Khurasani group (we don't hear about it anymore by the way) and Nusrah Front. Does that mean by their own logic that the US had created Nusrah Front?