With sexualization, I mean the reaction that one has when seeing the desired sexual object. I guess that in some countries, their cultures may have softer reactions, while in others, a stronger reaction could even imply rape.
Anthropologists have shown that all cultures have the same "amount" and "intensity" of modesty, shame and sexual excitability. What differs are clothing and behavioral habits, and therefore what is considered modest, what causes shame, and what causes sexual arousal.
The most extensive meta-analytic study on this topic is Hans-Peter Duerr's five volume Der Mythos vom Zivilisationsprozeß [The Myth of the Civilizing Process] (1988-2002), in which he collects and interprets ethnological, archaelogical and sociological research from all cultures and times regarding nudity and shame, intimity, obscenity and violence, eroticism, and defecation, in a reply to Norbert Elias' famous The Civilizing Process (1939).
You can think of the variation in modesty and sexualization over cultures as a border of the public display of the body that can be moved along a continuum from the eyes (burqa)
via the extremities (Victorians had to cover their legs)
more and more towards the center of the body (swimsuit)
narrowing down to the secondary sex characteristics (bikini)
the genitals (penis sheath or female modesty girdle [pictured below])
and finally the male glans (kynodesme) and the inside of the female labia
That peoples that live totally nude are not without shame and modesty can be seen from their social rules and the reactions to their transgression that Duerr reports. A telling example is how the girls of one naked tribe are not allowed to sit with their legs spread (so the insides of the labia don't become visible to the men), how the men attempt to catch a glimpse while the girls and women go about their day and react with excitement when they manage to see something forbidden, and how girls are being ridiculed if this happens. This is much the same as how we act with short skirts, the blowing wind and candid street photography.
Duerr lists page after page after page of research showing examples similar to this and to the one you gave in your comment (desexualized breasts). Unfortunately I don't know of a good English language overview so I can only recommend that you follow Nick's links and research tipps, if you want to get more deeply into this hotly debated area.