There was mino EMP damage to Hawaii, from down range US nuclear test, Starfish Prime of a 1.6 megaton nuclear device exploded 250miles up at a 10degree angle 1400nm W-SW of Hawaii. 300 streetlights went out and a radiotelephone link was shut down. 998 miles from the center blast 250 miles up. This was in 1962, and has been used by HI to justify all kinds of federal spending for civilian infrastructure.
Actuality is the the US Gov military sites are in need of hardening, comm links and such (or so it is said). EMP generated directly overhead would create much more damage than the 1962 atmospheric test, if done with weapon designed to specifically do this.
“One Second After”— William Fortschen foreward by Newt Gingrich. Firearms will still work. Ammo would have to be hand loaded.
Military bases should already be hardened against EMP.