The exceptions are men and women who have realized that it isn't easy to control infants and a good mother will do what has to be done. Not so disgusting from my point of view (and I'm a guy in my 20's with no kids).
I personally have no problems with breastfeeding, and I'm dubious of the "omg Americans flip out when they see it" implications above, but "naturalness" is not not really the reason something is ok to do in public or not.
The US is a country of immigrants, and if you look at the history - immigrant groups tend to be pretty dang religious. Pilgrims and Puritans, Africans embraced Christianity with zeal because of their circumstances. Later waves: Irish & Italian Catholics, German Protestants, European Jews; all very religious. And modern immigrant groups, Latin Americans, Koreans, Indians, etc. can all be quite conservative. Religion and culture intertwine because people tend to hang out with their own in the beginning - and the place to find them is usually at a church/temple/whatev. I guess it's like the old lunch table theory, you'll prefer to hang out with people that you think are more like you.
[edit] And to extrapolate this to the current topic, the presenter's greatest sin in the eyes of many US'ians is not his gratuitous use of sexual imagery to convey a point, but his complete lack of tact when doing so.