Depending on exactly what is hit, things could get very chaotic, at least in places, and hopefully for only a short time. You might not see FEMA for a while (nothing new there), but there is a National Guard Armory everywhere, so I suspect that you would see green (or tan) trucks all over the place. In the past I have seen military water buffalos show up at a natural disaster within hours, and bottled water from breweries in well under 24 hours. A circus tent set up as a chow hall, with food service provided by the military, the American Red Cross, Salation Army, even major fast food chain stores within a decent commute time. Law enforcement agencies, at least in CA, have a mutual aid plan in effect, so officers from one agencies can be moved into other jurisdictions on fairly short notice.

A lot would of course depend on the nature of, location of, and size of the "disaster." Roads that are impassible are impassible, greatly complicating things. Helicopters can only carry so much...