2. The idea of constructing a road that would be used exclusively for the delivery of mail without access by any other user was unheard of -- even in the 1790s.
3. I don't have a problem with privately-owned roads, but there are major flaws in that whole concept and there's a good reason why many of the toll roads that have been sold off to private investors in the last decade have turned into financial disasters.
False premise. One can establish such roads by law (e.g. desired routes) but have the private sector build and maintain them afterwards. Same with post offices, where charters are issued to private owner/operators.
The private sector owned and operated (and still does) huge interstate railroad networks; the same can be applied to interstate highways. No need to gouge people for taxes to fill a “trust fund” whose end is questionable, never mind being a Ponzi scheme in and of itself. There are no flaws with the concept of privately-owned roadways whatsoever, other than the government regarding it as a flaw when they want control of it. No toll roads given over to private operators have become “financial disasters” either—the financial disaster was having them “free” to begin with, and the trust fund is exemplary of the real disaster.