Not so much worried about our military stuff (most of that is shielded to some degree) but the havoc wrought on the electrical systems from the internet to banking to services production would be enormous.
Back in the 80s I remember reading a strategy paper that said the next big war would start with a huge nuke going off in the stratosphere and frying our electronics. Today, it would be even worse if it happened.
The damage would be staggering.