In the opening scene (set in New York), a soldier is told by a sergeant to put his match and cigarette out. The sergeant's stripes are of the British design, pointing down. Since this is a US Army sergeant, the stripes should be pointing up.
There is no evidence that German saboteurs were active in Halifax during the war.
In his spiel early in the show, the newsboy mentions Billy Bishop earning the Victoria Cross.
Bishop earned his Victoria Cross in June of 1917, so by December this would be old news.
The first scene shows a man picking up a box of explosives. The box is obviously empty.