The problem for America is that moneyed interests (big car manufacturers) would frequently sabotage or otherwise salt the earth for public transportation projects.

One immediate one off the top of my head is the Long Island Expressway: when it was constructed, it was built in mostly-undeveloped or under-developed land, and space could have been reserved for a rail line running parallel to the highway.

Another is less obvious: the Hudson-Bergen Light Rail line in northern NJ was constructed in the late 90s and early 00s, including a disused rail right-of-way that went from the southern part of Jersey City to the southern tip of Bayonne, near the Bayonne Bridge that connects to Staten Island (a notorious transit desert). While there were plans to extend the light rail line when the bridge was raised in the late 00s, it was decided against, even though it would've been a boon to all three cities/boroughs.