You may not know this.

IS, ISIL and ISIS are groups that I have been advised are paid for by Saudi Arabia. 

Their function is to stem the rise of Iranian power.

However, in doing so, if they succeed America will have to face Salafist Extreme Fundamentalist Islamism, a.k.a. Saudi Wahabism.

If IS goes down America will have to face Bashir al Assad and a Iran.

This is known as being caught between a rock and a hard place.

The only way to solve the problem is to do a Genghis Khan. This, equivalently is to go riding in with all the Abram tanks that the US has with the entire US drone air force, with the entire American Army invading Syria and all special forces to utterly subjugate all Syria. 

US military rule will apply over all Syria with these Genghis Khan rules of engagement;
         1. If in the city there is rebellion of any description, everyone
             within 5 city blocks of such an event are to be eliminated.
         2. In the country if there is an ambush, all human life with 10 
             square miles of the attack are to be eliminated.
         3. the US military governor and whoever he delegates to, will              have full and ultimate discretionary power over life and                    death
         4. there will be no such thing as appeals to the US supreme                  Court
         5. all citizens of Syria are to return to Syria and their assets 
             will be restored to them
         6. all citizens of Syria are to swear fealty and allegiance to 
             the US military governor.
         7. only the US military governor may release him from this                  oath
         8. it is death to breath this oat to the US military governor
         9. civilian life is to be the norm.