Subways are pretty much exclusively built in the cities, and the US doesn’t lack cities. The same is true for most countries.
Subways are pretty much exclusively built in the cities
Not just any city. Dense cities. Cities that are so densely populated that it would be /impossible/ for every person to move around in a car. Countless US cities are not even close to crossing that threshold. It just makes no sense to look at nationwide per capita on this. Only a city by city comparison of like with like population density is sensible.
(edit)
There is a baby elephant in the room that needs mention: US cities are designed with shitty zoning plans. They are designed so that each person on avg needs to travel more distance per commute to accomplish the same tasks (work and groceries). This heightens the congestion per capita. So ideally we would calculate daily net commute distance needed per capita plotted against subway track per capita for cities of comparable people per m². Which would embarrass US city mayors even more.
except the US also has some of the largest cities in the world lol, NYC alone should be churning out new subways like crazy
By size, you are referring more specifically to area. Area while neglecting population is inversely proportional to population density¹. But even apart from that – how does that support the claim that it’s sensible to disregard cities and just look per capita nationwide? NYC should be compared as a single whole city against other cities of comparable population density. Area does not matter as an independent variable on its own. What would the point be to blur NYC into a nationwide track per capita?
BTW, NYC has a subway system. I’ve used it a few times and it was not even close to being overcrowded but maybe I had lucky timing. Are you saying more track is needed there?
¹ population density: heads per m²