Its a bit misleading comparing Amtrak (which owns only about 1,000 KM of the tracks it uses) with Switzerland (which has over 3,000 km of track) and then the amount of tracks in the US total (over 250,000 km). Scale for national train travel is a big problem, hence why Amtrak is mostly reliant on renting time on shipping company's tracks. The makes the biggest problem with Amtrak not that people wouldn't use it, but its not even a comparable option excepting in the NE US where commuting may be a 'short' time investment. I once looked at visiting someone in the southwest US (about a 4 hour plane trip) and to get there on Amtrak would be a 3 day trip with an overnight stop in Washington DC and then another in Chicago.
That said, its not unfair to say that US people got led down the garden path in 1939 with respect to cars. Our city recently spent a lot of money to install a short trip street car after 60 years earlier tearing up their original street car lines in favor of cars-cars-cars.