I don't think that lack of A/C due to lack of electricity is going to change that since that disparity has been true since before A/C. It is basically the fact that heat can be alleviated rather easily, adapted to, etc, but cold wears you down.
I think you are right when referring to the NE. Winter is the killer. Here in the South summer is the killer. We don’t get that cold here and it only lasts for 3 mos.