My first response would be: any survey has a minority of folks believing silly stuff.
My second response would be: hey, wait, these kids might be really sharp. The Canadian newspapers, after all, keep talking about unaccountable Stephen Harper is. He has cut down quite dramatically on appearing at Question Period, which as the astute American 8th grader knows is a key form of holding the PM to account. Checks and balances? That is an American thing. With party discipline, the Prime Minister in a Westminister system, chock full of crown prerogatives, is damn near dictatorial some would say. And those some? American eight graders!
A key part of this answer was driven by an understanding (flawed or accurate) about the role of the military in Canada--that the military dominates the political scene. Given the mythology that the Canadian Forces duped the civilians into the Kandahar mission,* perhaps the Americans are just buying into this view.
*Tis a myth I address and attack in my forthcoming book: Adapting in the Dust: Learning Lessons from Canada's War in Afghanistan.So, one could look at this survey as suggesting that American school kids are sharp and well informed.... oh, right, never mind.