A nephew just back from service in the USAF spoke about some newer technologies that the US used to shut down power grids in Iraq and Kosivo. basically a big bundle of carbon fiber conductors, which would deploy out of the slip stream of device and hit a power station or substation or powerline and just cause all the circuit breakers to trip. would not blow anything up. but would just blow the fuses. aparently worked very well, but this was confined to small areas not vast territories. One of the aims of the war plan was to not destroy the infrastructure, just to tie it up.
As per the Senators claim of a scud attack, If launched from a disguised platform, a frieghter as he claims the BG's have then reaching hte continental US would be possible. And knocking out the US power grid in the senators mind means dropping Boston, NYC, phila, Baltimore, DC and the Carolina banking centers offline. or the Western strip from SD to SF.
He does not care if peoria has power or workable PC's for him all that counts is the business districts and yes that could happen with one emp.
The last big black out went from Nova Scotia to Savanah. as far west as Columbus. Think about that, power plants as far west as Chicago were tripped off line when the demand of the grid exceeded what was available in hte East. Until manual controls were instituted blocking off demand from outside of the general area, no one could restart, that is how the grid works.