I remember reading an article that said that fascism wasn't Hitler's creation, but a movement created by the Great War. Mussolini was its creator in a certain way.
Anyway, the article said that even if Hitler is not there, a fascist movement will eventualy rise. It won't probably be nazism, but will likely push for a remilitarization of Germany to make it a Great Power once more. Unless the new leader believes that Stab in the Back and Arian Supperiority crap too, the Social Darwinisn and anti-semitism won't be present, but the crazy nationalism will remain. Then, the butterflies are just to big. Does the new fascist party acquire actual power? Does Germany start another World War? As for the minor butterflies, the swastica wouldn't be seen as a symbol of a Genocide Dictadorship, but as a symbol of good luck in several religions.
As for Hitler himself, he may combat in World War I as an American Soldier, though wheter or not he identifies himself as American depends in his education and values.