As an American I'm not offended by the term Merica. I know too many people that use the joke too much to the point it's sort of overdone to the point it's not that funny anymore. I would be sort of annoyed if it was a Non-American that said that though. Sounds like a dumb move so I wouldn't like it being implied it's an American thing to do. People from all sorts of nationalities do stupid things like shoot rockets into a bubble shield, not just Americans, just like there are plenty of non-idiots of all sorts of nationalities. I think if anyone would be offended it'd be about that, not the fact the term Mercian was used.