It isn't only a matter of "frying" our own gear.
In addition, there would be more difficulty in monitoring the environment for some period of time.
Besides the political problems and such questions, why would we bother launching a nuke to kill a nuke when we are able simply shoot it down "with a bullet?"
Well, we might have to worry about the environment if we miss... say the "environment" of St. Louis, for instance.
I dunno, just seems to me when you're in that position, I'd have more confidence in overkill and wasting a few of our xthousand warheads than put my prayers in hitting a fly with a bb gun from five miles away.