It won't be done at all primarily because it would shove the entire world back economically at least hundreds of years, and that would include the West. The response might be total mobilization and massive military intervention in regions that have been on the edges, the marginal sort of non-supporters of terrorism who aren't exactly doing anything to eliminate terrorism. Make a list, it's probably close enough for planning purposes.
Perhaps. Still, I think you underestimate the horror of these weapons and what they can do. How about the nightmare sinario: They hit NY. We respond and make Iran and North Korea the 51st and 52nd states. A year later, they hit DC and Chicago. We bomb the hell out of Syria. 6 months later LA, and on and on.
Remember, these were built over 50 years ago with 1930's and 1940's technology.
I collect nuclear / cold war stuff, including films of blasts and photos. Below is a photo of the smallest above ground blast I have a picture of. It's 'only' 4KT. It's the Hornet test from March 12th, 1955 (exactly 49 years ago today). The picture was taken from 13 miles away. At this distance, if you were looking at the blast without eye protection, you would have been blinded. The heat from the blast would also be felt to the point of it being uncomfortable:
The lines of smoke rising in a pattern were smoke rockets set off right before the blast to measure the distortion in the atmosphere and to give perspective to how large the blast was.