I was born and spent my childhood in the UK but have spent the last 25+ years living in the USA.
In the UK I never lived more than a ten minute walk from a bus stop. The busses were every fifteen minutes, they were relatively clean and affordable. They were a mode of transport used by many people not just people who didn't have a car (the very young, very old or poor). We would go grocery shopping and carry the shopping back home on the bus in bags. There were also shops within an easy walk of all the different homes I lived in. That limited our groceries to what we could sensibly carry but gave us quite a bit of exercise.
In the US the nearest bus stop is a mile and a half from my house. It is on the grass at the side of a four lane highway with no bus shelter and you have to stand on the muddy, wet grass. It's six miles from home to work but there is no bus that goes directly there, despite it being just one left turn from getting on the bus to getting off. According to Google Maps it is an hour journey with 25 minutes of that being the walk to the bus stop. There are no grocery stores on the bus route. The closest you get is dropped off on the wrong side of a six lane wide highway then a half mile walk to the store. So cross the highway twice (at peril of death) and walk a mile.
In my car it is a ten minute drive to work. A detour to grocery and other shops is negligible and I can easily get what I want on the way home from work.
My (rambling) point is that the US towns and cities that I have experience of (mid-Atlantic states) are set up for cars, and lots of them. They are impossibly unfriendly for walkers and cyclists and the public transport has very poorly thought out routes. In fact, now that I think of it, the area where I live has changed quite a bit in the last 25 years with new shops, businesses and housing but the bus routes are exactly the same that they always were.