Ariana Grande burned herself badly in that donut shop … by bashing fat Americans, and now many people think that’s why she’s bailing on a huge concert event. Employees at a southern Cali donut shop were reportedly pissed because they said Ariana and her new BF licked donuts when no one was looking … which would’ve been nasty enough. But what’s pissed off even more people is what happened later in the vid — an employee brought out a tray of oversized donuts, and Ariana blurted … “What the f**k is that? I hate Americans. I hate America.” Boom! Fat shaming on a national scale. To be fair … she’s not the first to say it, but curiously Ariana announced yesterday she was dropping out of Major League Baseball’s All-Star concert this weekend. Her people say it’s because she had wisdom teeth removed on Monday.