How would those cars be refueled if all the refineries were toasted?
Cars still ran fine post Katrina. Gas availability was a big big big big problem however.
The question asked of me was how to get home from work if it happened in the middle of the day.
A NEMP strength is based on the height it is detonated - the higher it is, the more distance it covers. It is, however, regional in damage. If that region does not include Texas, power will stay on in Texas as it's grid is separate from the rest of the country. A major part of the country's gasoline comes from around Houston in Deer Park, Pasadena, and farther south in Texas City.
I feel sure the government would head to that part of the country FIRST to get those plants working and they would work if not in the damaged area.
If a NMEP went off over Los Angeles, that damage wouldn't extend to the east coast, it would die out and where it would die out would depend on how high the blast happened. It also does not take a high yield nuclear blast to accomplish that.