US lack of SW receivers in cars: potentially a 1930s-1940s decision to stop
'creeping socialism'...

I believe the decision on SW dates back that far, and there were certainly
adequate arguments for this based on the economies of scale at the time and
the overall quality of SW receivers.

The USSR broadcasting directly to the US in the early 1950s killed the
possibility of such a technical development.
(Vladivostok & Magadan Relay Stations ~ 1956, the Moscow region had 20 SW
relay stations by 1950 that could reach North America easily.)

Australia and NZ did not get SW in cars, not even tropical bands -- for
similar reasons.
The ABC (abc.net.au) did not have that much power over automakers in post
WWII Australia -- that is power to include tropical band reception for cars
sold in NT & Northern WA+QLD.