We’re not talking about why Seattle is far from Miami. American city sprawl is largely a recent phenomenon (post WWII) and was enabled by the rise of the personal automobile. Even the sprawl-iest of cities (Houston, TX) used to be respectably dense and walkable. The need for a car to achieve basic needs (groceries, school, work) is a phenomenon well less than 100 years old. America has this problem in part because it’s much younger than a lot of European cities, but it’s certainly not purely a function of topography.