Prior to electricity, people had a ways to get water, to dispose of waste and to distribute food and supplies. Those ways didn’t depend on electricity. Every home had its own water well or cistern system.
Very few people have their own water wells anymore. Much less any good way to provide clean potable water for the thousands of people in suburbia who would no longer have access to water out of their taps.
Lack of clean potable water would kill the most people, the fastest.
Then there’s the lack of food distrubution that doesn’t depend on electricity or fossil fuels...
“Very few people have their own water wells anymore.”
That depends on the state, in MI lots have a well.
You can drive a pipe in the ground most anywhere here and get water. All you need is a ‘well point’, pipe, and a maul, all available at the local hardware.
In some places in MI clean fresh water boils right out of the ground, you can connect that to your house with no need for a pump.
One of my brothers went 25 years with no electric pump on his well, clean fresh water in his house with plenty of water pressure(about 40 PSI). He added a pump when his pressure got a little lower, he still had good water flow.
Clean fresh water, wood heat, and a septic system, most in MI would do just fine.
There's also a lot of hunters that live here, hence there's guns and ammo.
The thing they would most need I would guess would be food and medical supplies more than anything else. Very few of them garden either.