It also doesn't acknowledge that a lot of that is just empty space. The US is ranked 180 of 242 nations in population density.
https://en.wikipedia.org/wiki/List_of_countries_and_dependencies_by_population_density
The US rail system has been bastardized since its inception, but this map is basically useless. The UK has 7x the population density as the US.
Are we sure the people doing the work aren't slave labor that just weren't yet human trafficked?