/johnny
I met a man who worked for the Department of Defense for many years and one of his areas of expertise was knowing how a solar flare or EMP attack could/would destroy our electronic systems in our major weapons and protecting them from those. The man said regarding the country’s electrical system the huge transformers going out could not be replaced for a very long time, many months. Yes, the country would be down for a very long time.
Taking out substations doesn't directly take out any generators. The big problem is that when the grid goes down, there can be no place to put the power. A nuclear plant has about 20 seconds to fire up diesel generators to run cooling pumps and to shut the plant down once it looses the grid. If not, it will overheat. That said, local plants can generate locally, grid or no grid. The grid balances power, it doesn't generate it. There certainly could be major disruptions. There are still enough ingenious people in this country that most wouldn't sit around and die, just because someone shot insulators off nine electrical substations.