The Carrington event was about 7 days, so one could assume this would affect EVERY country. So the hypothetical nation state here would need a ready-to-go plan

The Carrington event was about 7 days, so one could assume this would affect EVERY country. So the hypothetical nation state here would need a ready-to-go plan ready to roll out at any time, and the plan must assume the native country also has all electronics knocked out along with the adversarial country. Such an all-out attack by itself would turn the world against this aggressor, moreso since it exploited the event and was premeditated. I think it's unlikely, it would be a crazy thing to do. Now, who do I think might want to pull off something like this? A terrorist group could have a plan spooled up just waiting for this event. That, and I would expect some opportunists to appear as well.