If Starfish Prime had been a little lower and not 900 miles away, it would have had massive effects on Hawaii electronics, communications and electrical systems.
See how power-lines in the old USSR captured the EMP from one of their tests and fed back into the plant setting it on fire:
http://en.wikipedia.org/wiki/Electromagnetic_pulse
Thank you! I had heard about the tests in the USSR but didn’t know what kind of damage it did.