My father was a child during the depression years, and often said that he never knew it until he was an adult.
He was raised on a 125 acre farm and they produced most of what they required. At that time most of the USA was rural and there were many more small farms active than today.
An event such as that being speculated here would make the depression look like Sunday school.
Can you imagine the scenario after a few weeks without life as we are accustomed?
A few people living the rural life could survive and perhaps provide enough leadership and education to others to help them along, but how long would it be before they were threatened by the throngs from the cities who had nothing and along with that, no knowledge of how to make do?
It would be one hell of a mess.
I can live off the land if need be; I can get by without electricity if I must. And I've had a pretty good stock of ammunition in my closet for years that I rotate through and replenish like JD says for canned goods. We have no idea what might happen, but should be prepared for the worst as well as the best.