I'm pretty sure that for the Kimmel segments, they ask the interviewees different questions and later edit in a different question that makes the original answer seem funny.
I don't know about that, what I am pretty sure of is that for every funny answer, they have at least ten other boring "That person doesn't even exist" or "I don't know" replies.
I agree. Canadians love watching "the dumb Americans" on shows like this but you could get the exact same results going out onto Canadian streets. Many Canadians see themselves as intellectually superior to Americans because of our greater knowledge of their country, 80%+ of which knowledge I expect is from watching TV and movies.