Hitler's address, heard in the background, is not from his visit to Rome but from the 1934 Nuremberg Party Meeting, more particularly from his address to the German Youth on the third day. He's heard summoning them to be "strong and peaceful", "courageous and peace-loving".
In one scene, Antonietta is humming the song "Mamma" by Benjamino Gigli, but that wasn't released until two years later, in 1940.