Es gab keinen Hitlergruß in den USA an sich, warum sollte es auch? Das waren überwiegend deutschstämmige und von Rudolf Hess autorisierte Nazis vom German-American Bund, die aus ca. 25.000 Mitgliedern bestand.
Da irrst du dich gewaltig. Der Bellamy Salute wurde offiziell erst 1942 von dem "hand over heart" salute abgelöst.
https://en.wikipedia.org/wiki/Bellamy_salute
The Bellamy salute is the salute described by Francis Bellamy (1855–1931), Christian socialist minister and author, to accompany the American Pledge of Allegiance, which he had authored in 1892. During the period when it was used with the Pledge of Allegiance, it was sometimes known as the "flag salute". Later, during the 1920s and 1930s, Italian fascists and Nazisadopted a salute which was exactly the same except for the flag to which it was directed. This resulted in controversy over the use of the Bellamy salute in the United States. It was officially replaced by the hand-over-heart salute when Congress amended the Flag Code on December 22, 1942.
1915 (da war hitler noch ein kleiner unbekannter Straßenpenner)

