The hard truth is that in a prolonged national shutdown situation, folks depending on insulins and other vital meds will probably die after about 6 months. Cancers will take their course for there wouldn’t be any available treatments for them. Folks will have to be careful with cuts and injuries for infections will rage.
Famine will rage as folks won’t know how to grow crops and even if they could get plantings in at the right time, most seeds are hybrids and won’t be available in a national SHTF situation. All the suburb dwellers who currently like the ‘cute’ deer wandering thru their neighborhoods will find that more resourceful neighbors are culling those deer for food.
Local political situations will become very fluid with some regions coming under the control of warlords who aren’t very constitutional minded. There will be a lot of violence, a lot of misery and a lot of death.