Could it be caused by the aftermath of the flower power?
All that free love lead to children who ended up as single parents. The single mothers were naturally protective of their children, and the sons rather lacked male influence.
This, coupled with the popularity of lawsuits, could lead to schools and public facilities covering their collective asses and end group showers, which led to what we have today.
Could this be a possibility to men being embarrassed to expose their bodies because they have not learned from a young age that the human body in all its shapes and forms and sizes is natural?
There does not seem to be much similar embarrassment among the European boys and men.