That country is looooong gone (sadly). I’m sure there are pockets around the country where you can still have that experience. I don’t think the USA overall is a high trust society anymore. 

The only spots in my area where I see kids in packs similar to what I experienced growing up (leaving bikes unwatched, playing sports outside all day, talking to neighbors/strangers, not on a tablet by themselves, etc) are in gated neighborhoods (HOA).