This map of Sydney Mines, Nova Scotia, available at the Library of Congress site, was hand-drawn in 1907 and accessioned by the US War Department Military Information Division in 1908. It's very tempting to imagine it was drawn by a spy.
While no one would bother to seize Sydney Mines today, in 1907 the place had strategic importance. It was a growing industrial town located at the railhead on a major east coast harbour commanding the entrance to the Gulf of St Lawrence. The town was built on top of a large coal seam, and in those days naval ships burned coal. It was at the landfall of a transatlantic cable. And it was vulnerable, as the Royal Navy had left Halifax station in 1905.
The US made war in Cuba in 1898 and Mexico in 1914 and 1916. The Great White Fleet circumnavigated the globe from 1907 to 1909, projecting US power. Japan fought and defeated Russia in 1905, triggering a Communist uprising. France and Germany almost came to war that year. The world in those days was a big board game. Even Brazil, Argentina and Chile were engaged in a naval arms race.
To learn more about how to invade Canada, read about War Plan Red here.