The effects of an EMP pulse on the grid have been grossly exaggerated.

The grid is covered with lightning arrestors that will work for ANY excessive voltage.

Every transformer has a fuse or circuit breaker on its input side.

Induced volatage4 from electromagnetic waves does not have huge currents behind it.
Just voltage.

You need a loop to couple into the B side of the electromagnetic field.

The grid does not have all that many conductor loops for other reasons.