Why are they like this?

Protestant Presbyterian Puritans who went to America and spread their misanthropic values, which were schizoid versions of Judeo-Christian/Abrahamic values but more deranged, too much so for the European continent. America was known in its founding days as a den of charlatans, nutcases, swindlers, and religious lunatics who wanted to escape humanity and create some ill-defined utopia on a stolen continent. Hence Americans have such weird fixations; they hate nature because their Anglo-Saxon Puritan ancestors hated nature, they hate the human body for the same reason, and they glorify violence and irrational, aggressive behavior because it's what their media and inherited culture think is cool. Nothing about America is surprising once you understand who founded it.