Adult cycling in the 1930s-50s period in the US took place in pockets. Someone cited Boston as an example, and that's a very good one. Raleigh developed a special connection to Boston, particularly through the work of Hamilton Osgood and because of the university presence in an urban area. But in some other parts of the US, adult cycling on three speeds and similar utility bikes really never took off. This held true even after a bump in cycling during WWII because of gas rationing and the availability of utility bikes to workers in vital war industries (mostly major cities in the northeast and upper midwest). The automobile was America's primary love overall, though the pockets of adult utility cycling activity existed.
So I think the two big points are: (1) not all of the US was the same - three speed and similar utility bikes certainly had a following in some places and (2) on the whole, the automobile was America's primary love, especially in the late 1940s-50s era.