I don't think yank or limey is offensive, unless you try.
If I misjudged it and offended a cheeseburger-scoffing gun-toting would-be-speaking-Japanese-if-it-weren't-for-us Colonial lardarse, though, I'd apologise sooner than whinge about it.
( Newington, Thu 26 Jun 2008, 14:43, archived)