The two finger salute in the form of a "V", given by the Australians to the New Zealanders, is actually a vulgar gesture, which is derived as a result of the two countries being subjects of the British Empire. In turn, the origin of the gesture, possibly apocryphal, is an act of defiance by the British to the French, during the 100 Year War; Namely the French would cut off the fingers of British Archers, in order to incapacitate them.
Cas and Tulip, played by Joe Gilgun and Ruth Negga respectively, posed as the "Americans". Ruth is actually Irish and Joseph is English. Moreover, Dominic Cooper is a British subject (being English), as is Graham McTavish, The Saint of Killers (being Scottish). Furthermore, Pip Torrens and Noah Taylor, who play Herr Starr, and Adolf Hitler, respectively, are also English.
The waitress is named Sheila, Aussie slang for woman, (as "Bruce" is Aussie slang for man).
Australia was originally founded as a penal colony, in other words England would send over its convicts. The official sentencing for these convicts was known as "transportation."
When Herr Starr is on the phone you see him hang up the corded phone and dial the cordless. Then he is on the corded phone again.