For the United States, I agree mass Transit should be a much more prominent thing than it is, but suburbs and mass transit is difficult to deal with. 50% of the U.S. lives in suburbs, 20% of the U.S. lives in rural areas.
I couldn't live where I live without a car, and we literally have no mass transit. My nearest tiny grocery store is 3 miles away. I'm not putting a family of 4 on bicycles to make a run to the store to buy groceries, loading it on a bicycle, then hauling it home.
Part of the issue of mass transit, cities, and cars, is if I'm in a suburb 5 miles from a proper urban area with access to amenities, and I have no mass transit to get there, I have to take my car. And if I have my car when I get to the city, why would I park it to then take mass transit?
Mass transit actually has to become a realistic option for the 30% that live in a city before we even start to talk about mass transit for the other 70% of the U.S.