To add to Bill's commentary, U.S. capabilities are still miles ahead of the next competitor. Sure, the U.S. has its structural problems and a strong argument can be made that U.S. power relative to other states is declining, but there still is a long ways to go for other states to become peers. Much of the problem in the U.S. is self-imposed (political dysfunction, financial constraints, etc).

As for Iraq - well, unfortunately Bill is correct that some kind of action is required and that the Obama administration is trapped in the past. It's hard to see any other way to address the problem of ISIS without further commitments to Iraq's security. I see ISIS as the culmination of an escalation cycle of Al Qaeda, starting with the initial pre-9/11 spectacular attacks, and now with a movement that is relatively well-organized and disciplined. This is a problem two decades in the making and it will be some time, and will take more than just airstrikes, to resolve it.