It's a strategic thing. The bigger the stronghold the less the enemy can hope to penetrate. Nothing against the canadian people, but I beleive that's inevitable if the US was attacked by such a formitable opponent. The fact that their our allies only really means that we got their back. The U.S. military is way too strong for Canada to really have an effect in coming to our aid. They just don't compare military wise as far as funding and special training is concerned.
One thing you'd have to understand though, is that the Canadian Military of that era, would have far dwarfed that of its sorry shape today. Remember, the RCN, RCAF and Cdn. Army had a lot better resources, weapons and general esprit de corps, then that of your current "Canadian Forces".
Secondly, a 50's styled Canada, was a place of vast conservatism(unlike today), and many prominent Conservatives, though eager to fight a war against "Bolshevism", would have objected to a foreign power(even us, who are your ally) since this was also a time for National Identity for many Canadians....though you were still sons and daughters of Empire, you were beginning to distinguish yourselves from Old Mother England.