To achieve the generally-considered-ideal "15 minute" urban design without cars or public transit (which is what the parent post is advocating), you absolutely

To achieve the generally-considered-ideal "15 minute" urban design without cars or public transit (which is what the parent post is advocating), you absolutely require density higher than "single family separated townhome with a yard". You require shared walls and building up. WRT growth, Montana is roughly the size of Germany, but with 400k residents. It will take some 90+ years at the growth rate of 10% per decade to even break 1m residents, let alone Germany's 84m. That's well beyond my lifespan, though I'll do nothing to discourage the growth - that would be cruel. Even if I don't like living in an urban environment, I won't take that choice away from others.