Largely because children of the past two decades have been desensitized to violence, whether through film or TV, or, sadly, in their home lives, and therefore, to death. Especially to the deaths of the "other".

American "exceptionalism" has been taught for centuries and that allowed Christianity to be forced upon the "savages" who were here before white men and those white immigrants felt it perfectly reasonable to take ownership of land that natives believed belonged to everyone. What fools those savages are, to not even take "title of ownership" to designated areas of land!