The effects of an EMP blast can be managed. Low yield, low altitude blasts can limit the affected area so other countries are minimally effected. A lot of electronic devices that operate above 100 Mhz can survive an EMP if they are located at a reasonably far distance. One large yield blast at 300 miles up over St.Louis would be very nasty for everybody between the Rockies and the Appalachian mountains. The mountains would block a lot of the EMP signal. I don't think an EMP attack would be a one shot deal. That would leave the highly populated areas fairly unscathed. It would take 3 well placed blasts to devastate the US. One high altitude blast over the mid country and one 60 mile altitude blast over the mid Atlantic and mid Pacific coast. I think our method would be to use low yield, low altitude blast over all of NoKo's populated areas. Their rural areas are pretty much used to no electricity anyway. I'd like to think that NoKo isn't stupid enough to try an attack but I've learned over the years that people can be a lot stupider than one would think. They still vote for Democrats don't they?