We clearly differ on the USPS. FedEx, UPS, DHL, etc clearly provide superior service for overnight and courier service. Rural service could be solved - it simply has a cost. To your point, "as a country we've decided that it's in everyone's best interest to be able to go get mail." We have also decided to subsidize the cost of the service with metropolitan customers subsidizing the rural (similar to phone service). If the US used taxes to pay a FedEx, there would be better quality service at a lower cost.

Having the government provide the service introduces politics to the operation of running a business. Where should post offices be located, how often should mail be delivered, what products should we offer, should prices vary according to cost to delivery, etc. These issues make the USPS what it is today - a bureaucratic behemoth that is still delivering Christmas cards from 2020.

Of course the problems are solvable if you have desirable incentives. But as Pournelles Iron Law of Bureaucracy points out that the incentives to solve the problem are ALWAYS eventually replaced to preserve and grow the bureaucracy. And that’s why a universal, government solution is doomed to fail.

Funny you mention bad rural Internet considering that’s a problem technology and competition is about to solve.