@JTT,
I can't really speak to that. Presumably if the Nazis had triumphed in the 1940s, European literature would have changed as much as European history, and we would have had more emphasis placed on American misdeeds.
The Holocaust is unique in many minds because of the scale and scope of it: not only, as elsewhere, an army running amuck, not only settlers taking revenge attacks on native peoples, but a whole industrial killing machine involving large sectors of the nation, architects, builders, transportation managers and workers, police and army, with the rest of the population unable or unwilling to protest, most apparently buying the lie that
"Die Juden sind unser Unglueck." The national policy of mass murder, perhaps not unique, is unrivalled in scale and scope, outside of wartime, and this policy had its roots before war broke out.