This is in response to Ken's comment earlier "It's because we demand that the United States look after our defense for us"
This is a common sentiment on both sides of the border, that the US defends Canada's territorial interests, for free. Cause they're such nice people and all.
Wrong, wrong, wrong, wrong!
The US defends itself, and no one else. No part of the US Military Budget is devoted to defending Canada's territorial integrity. We get 0%. Which is as it should be.
We could debate how much implicit protection we get due to the overwhelming might of the US military, but that is straw man argument.
Why? Because there is no one threatening us.
From a historical perspective, the only country to threaten us physically in any substantial matter was the US itself (war of 1812). Then there is the practical matter of invasion. To invade Canada would require an amphibious invasion. This is no small matter. This requires some sort of air superiority over Canadian soil to support the invasion, large quantities of landing craft and the means to transport all this crap across either the Atlantic or the Pacific oceans. The only country with this capacity is the US itself (and possibly Britain).
Going back to the cold war, even though the Soviet threat was enough to keep many citizens awake at night, in reality, all of their military operations were limited to countries in Asia and Europe. Why? Because they were close to home, where reinforcements and materials are close at hand. If you look at the history of most conflicts, they are between immediate or close neighbors, not countries from different continents. Again, to look at history, the single greatest military threat to Canada, is the US itself. Not that this should keep us awake at night, as that threat is almost non-existent. But it shows how absurd other threats would be.
And finally, going back to the cold war, the only reason Canada was threatened in any way by the USSR was because of who our neighbour was, not because we were of strategic value in of ourselves.
And that is the problem with the argument relying on the implicit defense of Canada by the US, we are also implicitly threatened because our neighbor is the US.