Mario may be the international spokesman of a Kyoto, Japan-based company, but he's American, through and through. He's a Brooklyn, NY native plumber, as American as jazz, baseball, and Dominos' Pizza. That said, Mario is usually pretty reserved in his patriotism for his homeland, though he does wrap himself in the Stars and Stripes for the next Smash Bros. in a reference to an NES game many aren't aware of.
Released in 1991, NES Open Tournament Golf is one of Mario's earliest sporting adventures. The game takes Mario and Luigi on a tour of the world's best golf courses, with Princesses Peach and Daisy accompanying them. NES Open Tournament is the first game to make Luigi and Daisy a couple, and it's also the first game current-Nintendo president Satoru Iwata worked on from start to finish. Quite a lot of history for one USA-branded alt costume, huh?