Well they did the same thing with venezuela if you weren't paying attention. They were taking out whole electric power grids. So it's not exactly a secret.
Got any deep throat sources for this besides some out-of-options “president”?
So the obvious answer to gp is that the socialist government in power ruined the infrastructure and they are having to account for it by saying “the evil Yankee empire is the cause of these blackouts”.
Always go for the simple answer before looking for boogeymen.