The US had war plans against Canada. The Documentaries I saw explained it that the US was looking to instigate a world conflict against Britain to bring itself out of the depression and for a time they approached Weimar and later Nazi Germany in this scheme.
Even as late as 1943 (even with war declared) the US was still installing branch plants in Germany and the Occupied Territories (the Bush Family, the same ones as the later two Presidents, was alleged to had participated with this scheme. Along side other American bankers and industrialists).
American investment in Germany didn't really cease until 1943 when the US started Operation Husky (invasion of Sicily), so US policy was clear that the fighting in North Africa was really just some colonial war and the US could had pulled out.
http://en.wikipedia.org/wiki/War_Plan_RedGood example of how $Fiat leads to war. If Hitler didn't come along then the Americans would had simply invaded the British Empire and the bankers would had made a killing off that (seizing all the factories and bank reserves in Britain / Canada / Oceania and then issuing all those juicy contracts for reconstruction to predominately American firms).