there are a lot of people living in the pits of suburban sprawl who cannot electively stop using cars tomorrow

We have overproduced living space just like we've overproduced everything else. There are 32 million empty bedrooms and this is a conservative estimate of housing usage. There are plenty of smaller cities/towns, empty units, vacant lots, and oversize houses such that you could easily fit everyone within a short bicycle ride of their downtown. For someone who has a car, and either isn't trapped in debt or has reasonably okay job prospects, living in the suburbs is a choice.

People choose to continue living in suburbs partly because they're constrained from imagining anything else, and partly because they swallow the propaganda that this is what a good life means.

We could take 70% of the cars off the road within a year and still be just fine. (We proved this, pretty conclusively, in a dry run 6 years ago.)

Anybody who has the ability to move further than a regular commute's length has the prospects of living without a car, where 90% of what you need from a city is within a 30 minute bike ride and the rest is a 3-hour bus trip away, and where baseline costs (rent, water, electricity, phone bill, staple foods, produce) amount to 70 hours of low-wage work a month or less.

Most people (excepting those with chronic/acute illness) could live just fine on $30k USD per year. They don't do this because they're constantly chasing a bunch of optional things that you really don't need. Not everyone is eager to shed their car dependency, but for those that do, there's definitely a way.