So you'd need 6 of those highways converging on the middle of a city to compare to Tokyo's single train station. To make it really fun to solve, no rational city would allow that disastrous use of above-ground land, the parking for another 2m cars would be an engineering feat of note and you're dragging millions of tons of steel around for no reason. We haven't begun on emissions or need for fuel stops for those 2m cars.

Oh, and that's not the entirety of the Tokyo metro population, which is ~37m. The entire of Texas is ~29m-ish and that's spread out so far and wide they can afford to fuck around with 14 lane highways. The scale and solution are incomparable.