>This is how Europe does things.
This is also how America did things up until about the 1950s. From about that time period onward we didn't just build suburbs, we made them mandatory legally.
For instance, in your typical American suburb, you can't legally build a modern equivalent of a rowhouse; it might be too small to fit in the minimum lot size, its floor area ratio might exceed the ludicrously small allowed ratio, and it wouldn't have required side yards. Multistory apartments are mostly banned or, if they aren't, are required to sit on large lots so as to minimize their density. Then we tack on single-use zoning to ensure that nothing is within walking distance.
This would be bad, but manageable, if we could still build in our cities. Unfortunately our great cities have decided that their state at X point in time is the best humanity can achieve, so they have made it difficult to build new buildings. Our large cities in some cases have less housing than they used to due to urban freeways, misguided urban renewal, and the fires and riots of the tumultuous Civil Rights era.
>Basically, the mix of vehicles (cars, trains, driverless cars, whatever) is far less deterministic than the urban development patterns.
Yep. Many people fail to understand this; land use and transportation go hand in hand. Build sprawl, and you'll end up in traffic hell with no possible transit relief. Build dense development and, though congestion may be high, actual trip times can be shorter and alternative modes can flourish. It just so happens to also be vastly better for the environment.