Why are Americans afraid of a man in a speedo?

It is a good question I have often wondered about. I go to South America a lot and pretty much all men and boys wear speedo types and no one is uncomfortable about it. I would say there is definitely a homophobic aspect for men not liking them. As for women not liking them I am a bit mystified. As you say, they can show the bulge of their breasts, pretty much all the breast, cleavage etc, except the nipple and that is considered sexy. I have notices plenty of "camel toe" outlines of vagina lips at beaches and pools on girls of all ages and no one seems to care. But oh my god, the slight bulge of a penis and testicles is just disgusting. Not logical, Sure it is cultural, but the question is why is this embedded in American culture and not in European, Latin America, etc?