I think any answer to this has to involve two staples of American culture, cars and racism.

The prevalence of both has been a big detriment to rail initiatives. For whatever reason people have associated a nearby train station with crime and opening up the neighborhood to the "wrong people".

And the incredibly cheap and ubiquitous car culture (especially in the post-war period) provided the alternative. That of course interacts with the dramatic lack of density for new post-war suburban neighborhoods as well, which is a function of both issues mentioned (cars and racism) as well as the fact that the US does indeed (or did) have a whole lot of extra space compared to Europe.