What effect would a hydrogen bomb detonated at high enough altitude have on the power grid and solid state electronics?
You can expect any electronics with cables to get approx 50kV/m for E1 impulse to fail unless they have TVS type protection on those ports.
Power line responses are estimated by the LF E3 pulse at 85V/km.
https://en.m.wikipedia.org/wiki/Operation_Fishbowl
https://apps.dtic.mil/dtic/tr/fulltext/u2/1051492.pdf