I've read plenty of cables. I remember them bitching about Syria and listening to Saudi but I can't recall besides maybe giving some sort of ambitious April Glaspie type green light to Saudi Arabia (to support ISIS) anything like what the poster above is saying about ISIS.
The US very publicly supported the FSA, and while under the advisement and training of the CIA, the FSA fizzled out and most anti-Assad fighters left and joined Daesh or al Nusra.