First of all, EMPs don't really explode like a nuclear bomb. It releases alot of energy like a nuclear bomb. EMP's do not affect the body... that much.
They destroy things; they can injure your ears (permanent hearing damage).
Made the transportation of goods easier to get to the location that they need to be at. Also, allowed people to get to where they wanted to go.
overpopulation- which in the case of the united states would be very terrible indeed