I think you can make anything offensive (depends on delivery) but as an American I don't find it offensive in the slightest. If someone blew themselves up in a bubble shield and said "Merica" - I would laugh. Helps if you add "F&@? Yeah!" at the end... :) People take a lot of stuff way to serious these days. As long as it's not intentionally hurtful you have to be able to poke fun at yourself a little.