You're fighting cancer. Sure, the US can break all laws and go do a 100% clean sweep of that city, but the area around it will still be contaminated. US will have to leave eventually and this will open the door to new criminals who will simply see it as "free real estate."

If people themselves (the immune system, if you wish) don't make an effort like this woman did, no intervention will help them, Earthly or Divine alike.

At best the US can bunker up and make an effort to contain them.

Close to a trillion have been spent on Afghanistan for almost a decade. That much effort was needed to throw off an easily identifiable terrorist state. How will Afghanistan last until it collapses again? Because it's only a matter of time.