In 2017, the American Communittmy Survey showed that of the 46m households with 3+ people, approximately 44 million had 1 vehicle and 16 million had 3 or more vehicles.
If you see two parents and a child in America, it's more likely one of them thinks the moon landing is a hoax than that they do not own a car.
Who lives in a bubble?
https://factfinder.census.gov/bkmk/table/1.0/en/ACS/17_5YR/B...
And those stats aren't suitable for this purpose (they're undercounting my millions more), as there are many one parent households, plus many parents who live in a household with others but who don't own cars themselves.
2 person households, 38 million with 1+ cars, 2 million without.
4+ person households are almost as likely to have 4 or more cars as 0 or 1 cars.
Single person households are almost as likely to have 2 or more cars as no car at all. (The dominant number of vehicles by far is, of course, 1.)
Of the 85 million households with more than one person, only 3 million have no cars at all. You can "undercount" and adjust all you want, you're talking 5%, maybe 7% maximum of "parents without cars."
Of course it's possible, in a few scattered geographic areas with high density and convenient public transit. But that's not almost any of America.
You know that you can take strollers on buses and trains, right?