The "Largest U.S. Urban Regions" chart is likely referring to the U.S.'s 569 "Primary Statistical Areas": https://en.wikipedia.org/wiki/Statistical_area_(United_State...
The "Largest U.S. Urban Regions" chart is likely referring to the U.S.'s 569 "Primary Statistical Areas": https://en.wikipedia.org/wiki/Statistical_area_(United_State...