The confusion is that there are 50 states, and generally Americans do not know how many US territories there are. So "50 states" is understood as "all states,"

The confusion is that there are 50 states, and generally Americans do not know how many US territories there are. So "50 states" is understood as "all states," even though it could be 35 states and 15 territories for all we know. The 50 states part carries so much weight that one's mind may interpret it as "50 US States and X territories" with an implied X.