ISIS THREAT to US? No, not really. It is political gamesmanship though.

http://www.alternet.org/real-politics-behind-us-war?akid=12650.294211.oVVsZJ&rd=1&src=newsletter1029733&t=15

the solution to the puzzle lies in considerations that have nothing to do with a rational response to realities on the ground.
In fact, it is all about domestic political and bureaucratic interests.
Ostensibly the US-led military effort is aimed at “dismantling” the “Islamic State” as a threat to the stability of the Middle East and to US security. But no independent military or counter-terrorism analyst believes that the military force that is being applied in Iraq and Syria has even the slightest chance of achieving that objective.
As US diplomats freely acknowledged to journalist Reese Ehrlich, the airstrikes that the Obama administration is carrying out will not defeat the IS terrorists. And as Ehrlich elaborates, the United States has no allies who could conceivably take over the considerable territory IS now controls. The Pentagon has given up on the one Syrian military organisation once considered to be a candidate for US support – the Free Syrian Army.