Until recently, I used to believe that the American English and the UK English were the same language.
A childhood belief about foreign languages

others believed things like this
- I used to believe that the whole world spoke the same language- English.Anon
- I used to believe that english was the only real language and all the others were just made up after.Anon
- At the age of four I believed I was soooo smart. I spoke TWO languages...English AND American!— Melinda
- I used to believe that "elemeno P" was a certain kind of "P" found only in the English language. Anon
- I used to think that adults spoke an entirely different language (not English) when kids weren't around. — Swordfish
- I used to believe that, no matter what language other people spoke, that everyone thought in EnglishAnon