During the flamenco local scene, Cunningham claims that one of the reasons why Spain is neutral in the war is that the king's father is German (the other being that his wife is British). The king of the time (Alfonso XIII) was, indeed, married to a British princess but his father (Alfonso XII) wasn't German nor alive at the time. It was Alfonso XIII's mother who belonged to the royal family of one of the Central Powers, but she was Austrian, not German.
Cunningham's green Guardia Civil uniform and cape wasn't used until the 1920s. In 1917, the Guardia Civil wore navy blue.
When the Prague Spy is stuck in the closet, he is heard to say "I have to go wee wee". However, his mouth forms the words "I have to go to the bathroom".
After his rendezvous with the "blind man", Indy travels from Amsterdam to Prague. In the scene that follows and his suitcase accidentally opens, revealing several items of ladies' underwear, everyone but Indy speaks Dutch. This suggests that he is still in The Netherlands. However, the name of the station is "Belovar", which is located in Croatia. The people in this scene also look anything but Dutch nor does the location.