The gag about the antique anti-UK political cartoons is based on truth. These historic cartoons are located in the foyer of Franklin D. Roosevelt's home, King George VI viewed them them upon arriving in the foyer, and made a brief humorous remark to Roosevelt about the cartoons.
On June 11, 1939, the New York Times printed the menus for all of the meals served to the British royals during their visit to Hyde Park. As depicted in this movie, the picnic menu was as follows: Hot dogs, if weather permits. Beer and soft drinks. Cold ham from various States. Turkey, smoked and plain. Various salads. Baked Beans and brown bread. Doughnuts and ginger bread cookies. Coffee.