So, why do we need a supermarket? Is there any reason a supermarket couldn't be replaced with it's contingent parts? A butcher, a veggie shop, a convenience food shop, a pharmacy, a bakery, and a condiments shop?
I don't see why they have to be stapled together when separate works just fine. All of which could fairly practically be stocked individually by small light duty trucks, or even a bike with a decently sized trailer.
I also don't see why even if you staple everything together, a cargo tram wouldn't work. Have two, a passenger tram that works one route, and a cargo line that runs by the loading bays of local stores. They can be switched on and off the overarching infrastructure without interfering with each other.
It would be a paradigm shift for the US, but I fail to see how it would be an unworkable one.