How big a danger do you think this situation is...
I’m not an expert on our power distribution system. I do believe if someone really wanted to, they could easily take out electrical substations with coordinated attack (the high voltage transformers) just outside the typical city with 50 cal rifles from a distance and effectively take out the power to a city for days if not much longer. Especially if the attacker(s) know the internal structure of the transformers and therefore where to hit it so it can’t be easily repaired.