uh... most cities with a population greater than 100K?
There’s plenty of cities with 200-400k in population that have awful mass transit in the US. I previously worked in transit and have ridden systems all around the country. Even if a city has a bus system, routes and frequencies are very limited. You may have service Monday-Friday, but if you want to leave the house on the weekend, forget about it. If you work a shift outside of 9-5, as many low income folks do, the bus may not be running when you need to get to work or get home. As an example, look up transit service for any city outside of the three to five largest in the states of Florida, Georgia, Texas, Alabama, Mississippi, Louisiana, or South Carolina (just to name a few states) and see if you could get from a residential area outside the city center to shopping or a job on a weekend or at 7-8 PM at night.
Don’t get me wrong, I’m a huge advocate for mass transit (even more so if it is electrified) but outside of very large cities and liberal states willing to significantly fund transit service, going without a car is extremely difficult in the United States. A lot has to do with development patterns in the US that make serving communities by transit very difficult. Such development patterns also make alternatives liking biking not viable (due to distance) or extremely dangerous (due to road design) in many cases.
There are probably not more than 150-250 cities of any size in the US where a majority of the community can be accessed by mass transit seven days per with a reasonable span of service (heck, there’s some large cities that fail that requirement!). If transit can’t provide that, then people will need to seek alternate ways of getting around, which typically involve driving. I lived without a car for over a decade (in a much smaller place than DC), but it was only viable because it was a small northeastern city that was pretty compact and dense, so biking/walking was a viable alternative for many trips. I could easily continue to do so in DC and I only take my Model 3 out for a handful of trips a month, but I’m at a point in my life where I can afford to indulge in the technology as an option, rather than a necessity for day to day needs.