Not my belief, but my brother's. When he was around 12 and I 14, the subject of foreign accents came up in a discussion. At one point, I mentioned American accents. (We're American.) He looked confused, and said... "What? Americans don't HAVE an accent."
He had been assuming that people from England, Australia, etc. had to go out of their way to talk like that, and that the American accent was just the normal default way of talking.
A childhood belief about speaking

others believed things like this
- I used to believe that God looked exactly like the picture of Abraham Lincoln on an American penny.— Leah
- I used to think that AM and FM stood for "American Music" and "Foreign Music."— Sylvia Fowler
- I thought that all black people were African-AmericanAnon
- I used to believe that people who were african american were dark because they drank to much hot cocoa.Anon
- I used to believe that african american people were black because they ate too much CoCo Puffs— Jessica
- I used to believe that people were born with accents.Anon