>Suburbia exists because people want a quiet, relatively safe place for their kids to grow up.

No, that's not why modern sprawling suburbia exists. For most of American history, cities have been home to the middle class and wealthy. Not having to travel far for work or entertainment is a luxury, and middle class and wealthy Americans took advantage of it just like their world counterparts. The Bronx, for instance, was full of middle class families.

However, unlike many parts of the world, America had a terrible race problem. What do you do if you're a racist white American who holds that blacks are inferior, criminals, and going to rape your daughters after smoking the devil's weed? You enact legal prohibitions against them, of course. Squeeze them into one part of the city full of concentrated poverty.

But then courts started overturning legal prohibitions against minorities as attitudes against them improved. Schools were integrated. You even might have to work along side them. That's scary to racists who believed they were all criminals.

It's clear that racist covenants were on their way out, so directly mentioning race wasn't a good enough solution. But you still want race-based results. What do we do? Incomes amongst whites are higher today, and that was true back in the day. We can exploit that to keep blacks out, and as a bonus we can keep out the poor in general.

But we can't just slap up a 'no poors allowed' sign; that would be bad PR. What can we do?

Wait, I know! We can make it illegal to build housing that would be affordable for the poor. Since the poor are less likely to drive, we can also legally force all houses and businesses to cater to cars. If we couple that with laws that make it so our yards are big, and that houses, businesses, schools, etc. are all not near each other, then we can make it so that the poor can never afford these areas.

The beauty of this strategy is it allows co-opting non-racists. You're building the city of the future, as utopian 1950s urban planners thought. A world where no one has to walk because magical cars will save us from all social ills. Good schools, magically no traffic on the way to work, more space, who would be against that?

All we have to do is demolish large portions of urban neighborhoods, enact very restrictive zoning laws that exclude the poor and minorities, and then spend trillions (in current dollars) to build the interstates to make it all work.

Yeah, we'll wreck the environment, kill off passenger rail and public transit, cause urban blight, reduce economic growth, and drastically increase the price of housing (although that would take a generation or two to make it so the young couldn't afford housing, by which time we'll own housing anyways so that we can profit from that explosive housing price growth), but we'll finally never have to see a person with more melanin than us. It'll be great!

And that's how sprawling suburbs in America came about. There are harsh laws that enforce it, as otherwise it is not economical. Even just the laws that require free parking to be provided greatly increase the cost of construction and make many areas impossible to build in.

Yes, even Houston, the magical land without zoning (but many laws that are part of other cities' zoning codes, like minimum lot sizes, setbacks, parking requirements, etc.) has this. Even big cities like NYC, SF, Chicago, and DC got in on the utopian 50s vision.

You name your American city or town, and I will find the laws the force sprawling if they are online (not all towns have their zoning codes online). I can discuss at length the various enforcement mechanisms.