I don't think there is one beyond "hey look we all know this thing".

Americans: "We are a diverse patchwork of cultures and saying the US is one gigantic boring monoculture just because we share a common language is offensive"

Also Americans: hundreds of millions of people literally all relate to the same quirky element of childhood imposed through immense conformist institutions, can't even process the idea that other cultures exist that do not relate to this specific element.