Living off the land in a national incident or world wide incident is just about impossible for the first few years. Our food supply is highly centralized, and requires constant monitoring and cultivation (and also on GMO seed crop).
The land will be stripped clean. our big cities don't have farms. Without importation of vital food and vegetables, our country doesn't produce enough crops, and without transport, does not get to the town centers.
What a few have brought up ( post 281 and post 282): Yes we are safer and more secure than we have ever been; we have centralized security (police) centralized medicine (hospitals); centralized transportation (trains and airplanes, etc).
However, we are reliant on that system- 100 years ago, you protected your own home, and your own family. You treated your own ilnesses, and only called upon a doctor when all else failed. You maintained your own horses, your own stable, etc. I think life is much more comfortable and secure today, but it doesn't take much to disrupt our lives. 100 years ago, A hurricane (katrina) only affected some people. The rest of the country was unphased. Sandy wouldn't have been a big issue either. Rest of the country still operated.
Today, small events have rippling effects. "Bugging" out into the countryside is a romantic thought- living off the land, like your ancestors- except that there is too many people right now for that.
bug out vehicles are still a good idea- but so is staying put. the only reason to leave is if your location will be compromised.