generate questions: The 8- and 10-county definitions are not used for the greater Southern California Megaregion, one of the 11 megaregions of the United States. The megaregion's area is more expansive, extending east into Las Vegas, Nevada, and south across the Mexican border into Tijuana.
What is the name of the region that is not defined by the eight or 10 county definitions? {sep_token} How many megaregions are there in the United States? {sep_token} What is the name of the state that the megaregion expands to in the east? {sep_token} Which border does the megaregion extend over? {sep_token} What is the name of the area past the border that the megaregion extends into?