I found this fascinating post on metafiler with images. It is a crazy thing to think about. Possibly propaganda at its best? (or worst?)
More info with pictures...
"Metafilter's own JF Ptak has an interesting post on the Life magazine issue of March 2nd, 1942, readers of which were confronted by some startling maps detailing possible Axis invasion strategies for North America. There was invasion down the St. Lawrence valley, there was invasion via Trinidad, via Bermuda, full frontal west coast, and down the west coast as well - note the mapping of the large "fifth columns". As Ptak notes, maps such as these with huge arrows pointed menancingly at the American homeland were very much not the norm of the day.
In a second post on his marvellous site, Ptak discusses Life's dioramas of imaginary battles in the United States between Axis and Allied troops, and also outlines the development of the "Amerika" German heavy bomber. " Link Here