The range of effectiveeness of the sub-megaton airbursts are limited. North Korea at present does not have the warheads or the ICBMs required to affect more than a few local areas, and thosee IRBM or ICBM may very well be intercepted safely. More dangerous at present is an undetected suicide attack by a NORK submarine not suspected to exist. Such an attack could be directed at a seaport.
Even a small EMP blast in the NE would be horrendous. Densely populated area without clean water, food, heat or sanitation. Nightmare.
The ripple effect on the rest of the country would be felt for years.
There’s still a lot of military and civilian weapons manufactured in that area as well. Our military would begin to have resupply issues fairly quickly.
I’m not alone in suspecting any tech the norks have comes directly from the chicoms. Therefore, we need to make the assumption that if and when the chicoms want to emp us, the norks will magically develop that technology as well.
The purpose for nork is plausible deniability for the chicoms.