My father and mother bought an 80-acre farm between Reedsburg and Mauston, Wisconsin in 1968. This felt right to my father because our family had just moved to Hyde Park, Chicago and he felt a bit out of sorts. He himself had grown up on a farm in west-central Kansas. Hyde Park was way outside of his comfort zone.

Still, my dad was not pure farm boy. It was almost the 1970s and he was interested in looking sexy in 70s sorts of ways. One such way was getting deeply tanned all over and, to this end, wearing as little as possible. Even on the farm. Our farmer neighbors became very slowly habituated, for example, to the sight of my father mowing the lawn or cleaning out the barn wearing nothing but heavy work boots (with no socks) and a pair of khaki short-shorts, which were the result of cutting the legs off of his khaki pants.  By short-shorts I mean that the pockets hung well below the point at which the pant legs had been cut off.  He left the pockets intact because they were useful for holding nails and pipe tobacco.  Indeed, the only other thing that he wore was his pipe.

So, think “the Village People” and that was my father working on the farm. He believed himself to be sexy. Photos bear out this impression.

To the same sexy end, my father always wore Speedo swimsuits. Of course, so did every other male that I knew in the US in the 1970s. My father was different, though, in that he bucked the shift in fashions in the 1990s for men and boys to wear “jams”, or shorts that looked like huge tents.  My mother also turned her nose up at jams, saying “there is just too much fabric."
Long shorts are still the fashion in male swimwear in the US, and this nourishes the whole “Americans are prudes” cliché. This cliché is not consistent with the introduction of the Bikini for women in the US in the 1940s. According to histories of swimwear “The introduction of Reard’s bikini (named after Bikini Atoll in the South Pacific where atomic bomb testing had taken place) caused quite a stir in the United States…That was nothing, however to the reaction in predominantly Catholic European countries, including Italy and Spain, where the powers that be actually banned women from wearing bikinis on their beaches!” And of course, the creation of the bikini was less about sexiness or not as about economics. Apparently, shortly before the introduction of the bikini style, “the U.S. government had passed legislation for a ten percent reduction in the fabric content of woman’s swimwear as part of the war effort.”  
Yes, just as I learned in a social history class as a college student, the amount of material in fashion usually corresponds to the relative health of the economy. 
Jams, it turns out, came from the surfing world, not from a reaction to showing the male body. And now, American men are accustomed to that surfer style. In France, and other European countries, public swimming pools typically require that men wear Speedos. The motivation is not to see every man’s junk up close and personal, but rather in the service of hygiene. Here the reasoning is that if men wear jams or shorts, they’ll wear them all day, thus bringing into the water every germ they brushed past en route to the pool. This reasoning has implicit the idea that bodily germs produced as the Speedo is worn all day as underwear, are less icky in the pool than those acquired in public places such as tramways and benches. I suppose that is an empirical question.
Nevertheless, many American men have been surprised by this interdiction of jams in public pools in France and elsewhere. I can only imagine the clichés they generate to explain away their annoyance and the fact that they have to buy a Speedo or go home hot and sticky.
My four boys wear swim shorts in the US. But when we arrived in Munich a few days ago, and arrived to very elevated temperatures, we took immediately to the Freibad (outdoor pool). There, I noticed a shift. Even though anything goes in German Freibads, all four boys put on Speedos. 
This is the norm they learned growing up mostly in France.And I think that privately they like to show off their bodies.So, like my father, my boys will probably wear Speedos even after the style shifts in Europe. Indeed, the Bavarian response to jams is the creation (and very successful marketing) of lederhosen swim shorts. 
Ja Holla!