I think it's more a case of looking at each locality and seeing how people in that locality can live without bringing in things from outside. For instance, one might have an area that size of Orange County and see what can be made there.

The problem with being dependent on importing and transportation is that when supplies stop (pandemics, nuclear war, extreme weather events), the local area cannot and will not survive.

Basically, geograpical areas need to be self-sufficient