It's not only conceivable but it's the scenario most likely to happen (as far as big scale scenarios go)

Enemies don't need high-tech hard to get parts or components, the delivery system can be a short range (150 mile) missile launched 50 miles off the coast from almost any 50ft > vessel

A time coordinated attack from vessels off the east and west coasts could paralyze the country in a matter of minutes placing the affected areas back to the 1700's