In OTL, there's a strict separation of urban and suburban rail in North America (unlike in Germany, or Japan); even today there's a culture in favored quarter suburbs of New York that urban rail is for the poor and well-off suburbanites only take commuter rail and only at rush hour, and this was even more intense in the Mad Men era.
The upshot is that if New York had not built urban rail separate from suburban rail and instead built a combined system, as was proposed multiple times in the 1880s and 90s, the urban rail network would look pretty similar to OTL's, but the postwar view of what modern transportation is like would have been different enough to result in German-style transport politics (i.e. cars-and-trains, not just cars). The TL has US transit mode share bottoming at 20%, whereas Germany's bottomed in the teens, but the US has bigger metro areas than Germany and started building freeways later.