The EMP might already be in orbit. If the NK satellite is an EMP, we couldn’t stop it.
The only thing that gives me pause about how effective an EMP would be is the Cold War. We and the Soviets had thousands upon thousands of nukes. Why so many if just one could destroy us and knock us back into the 1700’s, resulting in the deaths of two thirds of the population through starvation, exposure to the elements, lack of medical care, medicines, etc. And do it without covering the planet with clouds of radiation.
How many of our nukes were developed BEFORE electronics were so critical to national survival?