Trouble is, when you need to get to the middle of nowhere is when you need transportation. If you stay within the densely populated areas where the people live you can walk. That's why people stopped living in rural areas after all; so that one didn't have to rely on transportation. Don't forget that rural areas had trains back before the urbanization movement! Passenger rail in the US died out because people moved closer together so that they didn't need mechanized travel.

The Netherlands, while technically highly urbanized, has remained more like a bunch of small towns instead of a few highly populated cities like as is seen in the US, so it is much closer to the rural days of yore when the US was able to support a comprehensive, nation-wide passenger rail system.