• how physically close people in that place interact

• dense vs non-dense living/rate of urbanization

• differences in people's overall health

Montana isn't as hard hit per thousand people as NY, for instance, and less dense areas don't attract as many visitors via airports and such. The elderly as dying more from it. That's just fact. How physically close people get just seems like common sense and I don't have much to back that up otherwise.

I think social distancing protocols have mitigated the curve, but in the long run, it won't prove as significant as the other three points. It's basically just to slow the spread down and keep hospitals from getting overcrowded.

Same with the randomness of initial spread. In the long run, even the places that got hit later will be just as bad off. It's not like the places hit later are proving so far to be effectively learning from the mistakes of the places hit earlier.