The Census Bureau’s “urban” is “not rural.” Most people live in metro areas, but in suburban and exurban parts of those metro areas without the density to make public transit good enough to rely on.
> 80.7 percent of the U.S. population lived in urban areas as of the 2010 Census
"Urban areas" includes where I live, which is not dense enough for public transportation to work well. Reading the article you cited, it looks like about half of the population labeled "urban" by the Census Bureau lives in areas that are like mine (or even less dense).
> which is not dense enough for public transportation to work well
You lose me here. I live in a major metro area and public transportation works fine, even out into the suburbs where it is not as dense, but the public transit spokes out to the major hubs and people drive to those transit stations and park for the day.
Public transportation works for the vast majority of the country.
https://www.citylab.com/equity/2012/03/us-urban-population-w...
I assume that number has only gone up since 2010.