What America might look like if it went back to medievalism.
This is a very well thought out (IMO) video of how America might look if restricted to medieval technology.
Although not strictly prepper related, I think there is a large amount of overlap and at least good thought experiment.
This takes into account things like water supply, genetics, culture, transportation, etc, applied as successive filters over an existing map I think the process works pretty well for creating a plausible breakdown.
Author: invalid@example.com (Darin lee)
