Labour-labor, theatre-theater, jewellery, jewelry… If you find the inconsistencies in spelling between American and Anglo-English irritating, let me tell you, it could have been much, MUCH worse!
My awareness of British vs American spellings began way back in Grade One. I was just learning to read and brought a picture book home from school that featured two adorable kittens and cans of paint. The word “color” in it surprised me, because I was pretty sure that wasn’t how you spelled that word. Then someone (parent? teacher?) told me that both spellings were correct. Wait… WHAT? Mind blown.