I don't think the US tries to control Canada like a vassal. It's an unfair portrayal of their common history. Canada is basically the parts of British interest in North America that that revolutionary war failed to reach or aquire in post war negotiations. Benedict Arnold, following Washingtons plan, was defeated in Quebec after all. The US influences Canada more than Canada influences the US because its population is 10x. If the situation were reversed and Canada had all the northern states of the US their relationship would be the same.