Click somewhere on the map and a nuclear missile will hit there and explode.

You can set the size of the shock wave in the parameters of a nuclear strike.
(if you set it to 0, the shock wave only affects the dynamic parts of the map. for example: vehicles, AI enemies, ragdolls, props and dynamic creations.)

You can also aim and launch nuclear missiles from a B-29 Superfortress bomber that flies over the map.

Maps in screenshots:

Oak Ridge, Micro Metropolis, Colossus Attack, Muratori Beach