How Hitler's worldview shaped the American declaration

How much did Hitler's worldview affect his decision to go to war with the United States?

It affected the decision heavily because Hitler and Mussolini consulted narrowly and filtered strategy through their own ideological assumptions.

Neither leader sought broad advice before declaring war. That narrow consultation left each dictator's ideological assumptions unusually exposed in national strategy. Wider Italian discussion might have revealed substantial opposition to an American war and even threatened Mussolini's position. Hitler's worldview likewise remained inseparable from his assessment of the United States because few competing judgments entered the decision.