This is a really interesting podcast reexamining the causes of the Holocaust. The thesis is that it was more about scarcity of resources than anything else. It's really pretty eye-opening.
http://warisboring.com/articles/how-...-happen-again/
By extension, this thesis could explain the rise of New America in the T2KU.
For a more contemporary application, the author posits that global climate change could very well create another holocaust-like situation as increasing scarcity resources leads to migration and ethnic conflict. One can already see this happening in Darfur and the "Fertile Crescent".
Give it a listen.