It is most certainly not. The inefficiency of USPS doesn't speak to the inherent inability for buses, trains, postal services and internet providers need to be subsidised. That it a huge claim you've made, one link on the inefficiency of USPS(a government funded service...) does not suffice.

The inefficiency of the USPS speaks to the inefficiency of government services. They've lost $47bn over 10 years. Why? Because they have no incentive to care about their business model, because they can be apparently infinitely supplied by taxpayers.