We don't say arseholes, either. We don't drop the letter h on our words, so edit and obelus wouldn't work (if, in fact, that's what they're supposed to be, if not, I don't get those). Most people in the US probably don't know what Sinn Feinn is (and while I do know what it is, I don't get the joke).

I'm sure it's very funny in the UK and the Republic of Ireland, though.