Our war hawks like to think that we are ready to kick som Arab butt but the reality is that as a nation we are highly casualty averse. Or multi-deployment effort in Iraq and Afghanistan was carried out by less th 1%of our population yet the casualties deeply shocked the American people and will be with us for another forty or fifty years.
The Sunni world is convulsed in a great civil war. None of the combatants are pro-American or want to be our allies, although some will gladly take our guns and money in hopes of winning their struggle. The combatants are supported by various Muslim individuals, group and nations around the world. None of the players have the capability to successfully engage the USA in conventional warfare.
It is already clear that the response to American intervention in the Sunni civil war will be terrorist attacks on targets of opportunity wherever and whatever they may be. Given America's position in today's global economy, there will always be targets available and the cost of defense will continue to be grossly disproportionate to the cost of attack.
Isolated attacks such as the latest in San Bernadio cost less than one-thousandth of coordinated, intrnational attacks like that on 9/11 but are, arguably, in the same scale in terms of the terror the yield. One hundredth effect for on thousandth the effort is a great bargain ratio.