When we managed 4%, and more, the public attitude was much, much different. In the late 1940s and throughout the 1950s Canada was, overwhelmingly pro-American and anti-communist - the Berlin Blockade and Korean War had shown us, clearly, that Stalin was a real, measurable threat to our own peace and security.
That began to change in the 1960s - first, the information universe grew, we heard and saw more and more diverse "voices." The Vietnam War had a HUGE impact. By the mid 1960s Canadian young people were out marching, shouting "Hey, Hey LBJ! How many kids did you kill today?" We had no stake in the war but our public attitudes were very largely shaped by the US media and by 1968 even "old school" Walter Cronkite had tureens against the war.
In Canada, Pierre Trudeau told us that America was, at least, as big a threat to world peace and security as was the USSR; his 1970 Foreign Policy White Paper almost totally ignored the USA and said that Canada's domestic problems (Quebec, language, the environment) were our only really important concerns. His message was enticing; he said, de facto, the USA must, for its own strategic reasons defend us, we ned not bother. He had already cut our NATO commitment and the country was with him. All of Brian Mulroney, Paul Martin Jr and Stephen Harper wanted to turn Canada round but none, not even Mulroney after his landslide 1984 election victory (50%+ of the popular vote), had enough political capital.