I am not expert in the field and know little more than the average joe, but I do have a electrical background. Communications is easy to disrupt, but harder to destroy.
Older stuff was not well shielded, but the late model equipment is hardened a bit, even the civilian stuff. We had a lot of issues with sun spots over the years and they made it much better.
Car electronics are another story. There is no ground path to the earth, and the excess voltage generated by a EMP would require aviation shielding.
Anyhoo, I could see a metro area going dark, or even a large portion of the power grid for a time, until they got the controls reset and the generators back in sync, but the damage would not be permanent from a air burst of tactical or medium size. I don't think the NK's, terrorists or Iranians could field anything bigger and they could get better results on the ground. As to the big boys, they could take us out but it would take a biggun......IMO.