Answer
the US president is the head of government and the head of state (he runs the government and the military)
the Canadian PM is head of government only. The head of state in Canada is none other then the queen... of ENGLAND!
also the US federal gov. has some different dutys then the Canadian gov.
US presedents have to leave after 2 four year terms Canada is elections approx every 4 years unless a non confidence vote or dissolution of the house of commons occurs