There are some small microwave devices now that interrupt communication via any radio wave, and potentially damage electronics that use magnetism in any way. I know little however of EMP's though I bet our military either has or is working on such a thing.
To blanket an area would disrupt too much. For instance, if we EMP's China, we would have nowhere to buy stuff from, and if they EMP'ed us, they would have no one to buy it!
But if we could target, we could snipe around and help build up the military complex some more....
Ben