It is true that modesty is not an exclusively US puritan ideal, but the US has a disproportionately strong cultural influence on other societies.

In my neck of the woods we are much more relaxed about nakedness, and find the scandals in the US around this topic amusing. But for instance the lengths at which for instance facebook goes to to avoid nipples and penises feels more like an overstep in cultural freedom.

"Modesty" is culturally defined in the first place. What you would consider "modest" today often would be extremely immodest a century ago. And, conversely, some societies don't consider nudity to be immodest in and of itself.