The timeliness of its release, just after the attack on Pearl Harbor in late 1941, helped the 'propaganda machine' of going to European battlegrounds overseas with a song that was a rousing theme song written years earlier for WW I - Over There. And a second song, You're a Grand Old Flag, contributed to morale-boosting, flag-waving patriotism and love of one's country. And it was the first time that a living US President (FDR in this case, played by Jack Young) was portrayed in a motion picture.
...FYI -
"Two drifters off to see the world. There's such a lot of world to see. . ."