I agree there should be a minimum age but much younger than 14. So much depends on the child. Some could be left alone with instructions and emergency contacts as young as even 8. Some 20 year olds have no business being left without supervision.
Howzabout we get the fucking government OUT OF THE BUSINESS OF THE FAMILY and let the parents decide. I was a free range kid who was told, "go outside and play until the streetlights come on." I had defined boundaries where I could (and would) roam freely. I didn't have instant two-way communications with the parental units. If I needed approval or had a change of plans, the quarter in my pocket and the phone booth on the corner meant I could reach home. I didn't need the quarter if I was at a friends house.
It was also the age where if I had more than three dinners a month at a friends house, I had to help my friend with his chores too.