Growing up in upstate NY, I used to believe that Canadian coins, which are accepted as legal tender here (except by banks), were accepted all over the United States. I was kind of surprised and embarrassed when I was visiting relatives in Mississippi, handed over a Canadian quarter to pay for something and the checkout girl stood there staring at it and going, "What the heck is this?"
A childhood belief about money

others believed things like this
- I used to believe that America was one of the states of the United States.— Limor
- i used to think France was in the united states
— TY - I used to think that Los Angeles took up half the United StatesAnon
- I used to believe that the United States were a planet, since I'm from another country.Anon
- I used to believe that the maps for the United States and Texas were identical.— JTexas
- I used to believe that the United States covered almost the entire planet.— RAB