Er, that's not really true. Lots of places that have good public transportation are not short on landmass. And the U.S., despite its large landmass, developed its own cities in very dense styles right up until the car became dominant. You can see this in every American town that has a "historic downtown". Prior to the car, the development pattern was large numbers of fairly dense developments, which were internally navigable by streetcar if they were large enough to require it, and which were connected to each other by railroad.

American cities _did_ make large public transit networks in the past - L.A. once had the largest streetcar network in the world - the thing was that it subsidized cars and made preferential rules for cars to the point of bankrupting the alternatives and then ripped them up. Those streetcars also supported lower-density developments on the periphery - "streetcar suburbs" - which today are still valuable and prized places to live because they are far more walkable than your typical cookie cutter car dependent suburb sprouting up today.

I feel that almost every city that has an "historic downtown" is now also quite a bit larger than what that area defines, and that prior to the car, most cities were developed to take advantage of geographical features that could make certain types of business more profitable or even just possible. If the density was mostly a function of timely access to these features, then it's entirely understandable why we abandoned it as soon as we had the option. And why city boundaries started to grow around the same time.

In what years was that system operating? Los Angles wildly expanded in size from 1912 to 1915, and it looks like most of those systems struggled to be profitable before this point and were only further hampered by the expansion in size and the low ridership of rural lines. It seemed they were unable to accurately match rail with demand in most cases.. and most rural/suburban people were already beginning to prefer cars.

> prior to the car, most cities were developed to take advantage of geographical features that could make certain types of business more profitable or even just possible.

Isn't this self-evident for any town? If the local geography offers nothing in the way of convenient mobility, natural resources, easy access to trade routes, or anything else worth taking advantage of, there's no point founding a town there. Towns need to build wealth to survive and grow. One distinct drawback of ripping up streetcars and making everyone depend on the car is that you have to level massive portions of your downtown to create parking, and you have to take away tons of public space from people to make room for all the traffic. LA did both of those things and it's why it's unique among U.S. cities of its size for being horrifically sprawly and difficult to navigate.

You also need to bear in mind that car-centric development is incredibly, wildly unprofitable, and is subsidized by taxpayers. Modern low density suburban developments require absolutely enormous quantities of expensive infrastructure - pipes, asphalt, power lines, waste collection, wastewater treatment, fire, police - massive upfront capital expenditures with massive long-term liabilities. The U.S. has collectively spent many hundreds of billions of dollars building and supporting infrastructure for the exclusive use of cars. The local taxpayer base rarely if ever is actually able to offset that cost which is why A) much of the funding is from state/federal grants and B) public debt is increasing without end.