As I said, I too see that but it's mainly been on film. I'm certain I've never seen that particular placement here in the time I've lived in the states. When I was assigned in various areas many years ago the furthest I saw was a mailbox attached to the home or beam/column near steps a few feet away from the front door.My understanding is that many properties in the US, especially rural ones don’t have all their mail delivered to the door. Certainly not on the TV I see here, where even in suburbia the box with a flag is popular at the end of the drive.
I think the Royail Mail do an excellent job of delivering to all UK addresses, no matter how remote.
I can believe what you say about Royal Mail.