Excellent examples: Melbourne and Adelaide in Australia. In fact, Adelaide is pretty spread out and suburban, but it still has a nicely laid out (if a bit dated) train network). Melbourne didn't ditch their trams and now have the largest network in the world (and they still have tons of suburbs with regional V-Lines reaching almost all of them).
If the tram networks hadn't been removed, we would have seen different priorities. Also, just because it's gone now, doesn't mean we shouldn't start fixing it. The amazing thing is when you do lay out rail, people tend to start building around them; including stores and housing. They have a an incredible impact on commerce simply by being laid down. There is a psychological impact of seeing the rails and seeing the trams pass at constant intervals that changes the way people think about transport.
I'm passionately in favor of your counterfactual. If we hadn't allowed so much low-density development, if we'd have kept and extended the streetcar lines, if we hadn't invested so much in automobile infrastructure, then we'd be in a much better position today.
But now we're faced with a confluence of factors that make getting to that counterfactual really, really hard. Those factors, collectively, are what I'm referring to when I say we're too "spread out."
"Spread out" isn't just about distance; it's about population size over a given area. It's about density, in other words.
Melbourne has 4.6M people in 3800 sq mi.
It has a tram/light rail network of over 160 miles of track on 24 separate routes, and nearly two thousand tram stops. It runs a network of nearly 500 trams, and carries 200 million passengers a year.
https://en.wikipedia.org/wiki/Trams_in_Melbourne#/media/File...
To give scale to that map, the radius of those routes (you can see something of a circle around the downtown area) from the city center averages about 15 miles (East Malvern, Box Hill, etc), and stretches near 25 miles at points.
Using your St Louis example and recognizing that certainly, not all of the Melbourne urban area is serviced by light rail, well over 700 sq mi is 'very well served'.
Yes, I agree that we should strive for higher population densities and that we shouldn't have invested so much in automobile infrastructure, but given that this is where we are, people will make rational decisions.
That's what I mean when I say that we're already too "spread out."
By the way, on the off chance anyone's interested, here's a map of those original streetcar lines:
https://www.google.com/maps/d/viewer?mid=1W809wsAmB9GR3ZvyII...
The region is now spread far, far beyond those original borders. Only about 300k of the 2.8 million residents of greater St. Louis currently live within those limits.
The historic streetcar network cannot be replicated today precisely because, yes, we are too spread out.