I’d add Montana, too. I just said Idaho, because I live near the border (minutes), and they can be pretty rugged. Also, James Rawles (who wrote “Patriots,” “How to Survive Anything,” etc.), wrote “Patriots” setting in Idaho, and suggest moving to Idaho, and they also passed a law making you able to pay property taxes in Precious Metals, so I’d say they’re pretty prepper friendly. But you are absolutely right, there are lots of places that a person could do well. I hate living in Zone 4 with 6-month winters, but I choose to because I do like the fact that the unprepared will head South, and not north!
If everyone in Idaho prepared even a little, and were willing to band together to defend it when SHTF then that would be perfect.