American historiography regarding itself is quite a bit different than some random thing you think people cite as the cause of World War 2.
Hate to break it to bud but Anschluss was in 38 before the war, and I've never heard anyone cite it as a cause, especially not here in America. I've heard Polish aggression, I've heard German invasion of Poland, I myself partially blame British expeditionary forces, some blame the rape of the Rhineland, some say that it's solely Germany's fault for invading France.
I have never, ever, in all my years of World War 2 revisionism, heard that the fucking Anschluss was the cause. And I believe FDR was a secret commie who chose to let the Kido Bitai hit Pearl Harbor, rather than give up a codebreaking advantage the US had. The wartime figure I most agree with? Father fucking Coughlin, and even I have never heard the Anschluss blamed.
If you want to blame something that occured before the war, you would blame the Spanish Republicans, or maybe, Stalin declaring war on "social democrats" in the comintern in 1928. There's no situation where Anschluss as the first cause makes sense. I've even heard the Germans blame the FRENCH REVOLUTION, but the Anschluss? This is new to me.