I can't be asked means I don't want to do it or I'm too lazy to do it. It's not just Americans who probably misunderstand these things. For a lot of Americans, our version of the language is like this little boutique sort of strange quaint little toy shop version of English. But if they hear us, they're hearing us. Our arse is just the British version and ass is the American version. We complain about people not understanding what we're saying, but really to a non British person or an on English speaker, but even non American. They're the things that drive me nuts.