Which of the cities used as examples in the articles are "sparse"? LA? Pittsburgh is one of the smaller ones listed and while the bus network there is very hub and spoke, it's also still semi usable.

But to call NYC, LA, Philly, Chicago, Minneapolis, Houston, etc sparse doesn't seem very accurate. Yes, LA is vast, but I wouldn't call it sparse.

LA is sparse by European standards, or rural by Asian standards.

http://www.demographia.com/db-worldua.pdf CTRL+F for "BUILT-UP URBAN AREAS BY URBAN POPULATION DENSITY: 2025"

America is the exception for population density in general.