According to this documentary, the first Hollywood anti-Nazi film was Confessions of a Nazi Spy (1939), made six years after Adolf Hitler came to power in Germany.
Van Johnson hosts this documentary and he himself was a star of the Hollywood World War II war movie. His movies about WW II have included Thirty Seconds Over Tokyo (1944); Battleground (1949); Command Decision (1948); Go for Broke! (1951); The Caine Mutiny (1954) ; A Guy Named Joe (1943); The White Cliffs of Dover (1944); The Last Blitzkrieg (1959); The Enemy General (1960) and Battle Squadron (See: La battaglia d'Inghilterra (1969)).
The documentary states that by 1944, weekly attendance at cinemas in the USA had increased from 55 million in 1941 to 100 million in 1944, maintaining that by 1944, two thirds of the nation went to the pictures every week.
Hollywood World War II movies made during the WW 2 have influenced many a later movie including Apocalypse Now (1979) and Star Wars: Episode IV - A New Hope (1977). Going Hollywood: The War Years (1988) says that these movies and others have "...borrowed from the techniques and cinematography used to depict the Second World War."
This documentary reports that two months after Italy surrendered in World War II, the Hollywood WW 2 movie Sahara (1943) was released with an Italian as a principal character - and a good guy. This was J. Carrol Naish playing Giuseppe in Sahara (1943).