EMP is over-rated. The Tzar bomb (50 megaton) did not wipe out the USSR’s power grid when it was tested. Now it wasn’t an air burst, but if all the hype about EMP was accurate, Moscow should have gone dark.
Suspect EMP is 99% hype and 1% real with a narrow area affect, which would be dead from radiation anyway. No demonstrateable proof that EMP works.
EMP is a line-of-sight weapon when detonated in space. 1MT 400 miles over Kansas takes out the North American power grid coast to coast. Period. Lower yield weapons are more effective than very high yield weapons. That 50MT weapon was not detonated in space. Russkies like their electricity.