Isn't the point of a 15 minute city that you can get anywhere within 15 minutes without a car?
(By the way, from a European standpoint it sounds really funny that 15 minute cities are not a reality for you. Like, why would you ever build a city differently in the first place?)
It's pretty disingenuous to claim that your city founded in 1300 has tight streets and isn't car-friendly because people in 1300 were really big on public transport.
And the answer is that cities grow descriptively rather than prescriptively. They generally add what is in demand/what they need piecemeal, and most US cities really grew in the 20th century.
That's why NYC, for example, has significantly better public transport than most of the nation - it's one of the oldest cities
This is also why moving to mass transit is a hard sell. It's expensive and there is less demonstrated need and more forethought behind the switchover.
There’s an few distinctions about American culture as it relates to car culture.
America had/has a lot of land
Much of this is/was vastly underdeveloped right outside of urban hubs, unlike Europe/related which benefits from a tighter interconnected network of cities that more immediately benefit from mass transit systems
In the US post-WWII middle class and privileged were often sold an idea of peaceful suburban lifestyles away from urbanized areas
Car manufacturers marketed this successfully as a way to encourage families away from city life and thus build a more solid reliance on their vehicles
City planning was therefore often built around a suburban-city sprawl rather than a cohesive urban community designed around efficiency
Like, why would you ever build a city differently in the first place?
Exactly. Unfortunately, in Australia, we tend to borrow stupid ideas from the US to make money and have sprawling suburbs with zero amenity.
For instance, we had a new suburbian development within 20km from the CBD with the promise of schools, community centres etc. in the early 2000s. When all the houses were bought and built, suddenly there's no money for amenities so they just sold the land to developers who then put more houses in. Now the only way to get anything you need is by car because there's no train or buses because it was supposed to be accessible by bike/walking but now isn't. And not to mention gridlock of vehicles looking to get out of the suburbs for food etc. out of the one intersection provided.
I would love 15min cities without cars for my country but the attitude to cars here is similar to the attitude about guns in the US.