I thought I would post my regional breakdown map. My goal was to give each region a similar physical area and number of survivors. I did this a long time ago and I will have a newer, sleeker version soon.
I debated for a long time keeping state borders intact but decided that if a pre-war command structure was still in place it was best to have a regional command deal direct with their state's structures. If states were no longer governed as a whole, regions might transfer off certain areas (like parts of Maryland Oklahoma and Michigan)
I believe that all my major commands are 60 miles away from a canon nuclear target (except New Jersey as there IIRC is not a single spot in New Jersey less than 30 miles), but I may have made this map before I did all those calculations. My newer map will fix that if that is the case.