You all do realize that suburbs existed before the invention of the car right? American infrastructure is bad but it’s not irredeemable, the assumption that we can’t provide public transportation to these places because of a lack of resources is malthusian. And sure some places like the American Southwest and Florida are legitimately over human population carrying capacity due to climate change but in general the earth as a whole isn’t, and cities like Amsterdam are just as unsustainable as Miami since even though has one of those le epic reddit notjustbikes cityskylines approved infrastructure, both are below the sea level.
I think in general our message should be abolish the need to own the automobile, any measures meant to limit car use should target the rich before the poor. And that trains are good, and that a high speed train across the United States would be a rather popular project in the eyes of even the chuds. And by god stop calling for the suburbs to be razed, stop trying to be zoomer Robert Moses.
Suburbs did not really exist before the invention of the car. However structures on the periphery of cities, as camps, colonies and other settlement areas did exist. Regularly reaching into the country site. Suburbs did become a specific concept in current usage and aren't suburbs of them and both aren't good.
Marx and Engels wrote in the Manifest of the Communist party that:
In later texts the abolishing of the distinctions became more important the "more equable distribution" took a back seat row and was rightfully critiqued.
What is it that interests you in your conception of sub urb? Do you live in one, do you project nature peace on it and community? Are you in a capitalist city and suffer from it, wishing for an utopian escape into the countryside/sub urb with the benefits of the city?
In any case I agree with your point about abolishing the need for an automobile, however that is a talking point urban planners and plenty liberals would accept with and movements like the 15 minute city (which gets critiqued form the right, right wing billionaires and car industrialists). However the way it would be done matters.
No lost suburb is worth a tear. People who cry about lost sub urbs don't cry about whole villages being destroyed by lignite mining.
That doesn't make it unsustainable. The consumption of its industries and the higher incomes play a larger role in that than the biking infrastructure. Which brings me to the point:
Suburbs are not efficient, no amount of public transports can save them. This is cause of the material conditions they create, only a radical re drafting of them (fusion of modern urban planing and "Commieblocks" or alike) could safe them. Then they wouldn't remain suburbs, though. The amount of roads in suburbs alone per person means they are a drag and rationally they are not a sustainable place to exist.
If you worry about the old poor pensioners without healthcare in suburbs that might be lost if suburbs are abolished you forget that they will be much better than now.