Read the book "One Second After".  It's a novel that addressed what would happen if the US was hit by an EMP.  It's pretty nasty.  If the electric grid gets fried it means no food, medicine or other essentials get delivered, no running water, no refrigeration, etc.  People turn into animals fighting for survival.  It's not that expensive to shield the grid from an EMP attack but, for whatever reason, Congress has ignored this vulnerability for a long time.