I’m not aware that EMP attacks are directional. The rocket in this case exploded at an altitude of approximately 44 miles which would seem to be capable of knocking out China and North Koreaas well as Japan, South Korea, etc. Now there is the chance that such a missile could be submarine launched off our west coast. That is if we would allow noisey, diesel subs close to our west coast. Just hitting Hawaii would bring a big response.
They have electric subs