The problem is that you underestimate how widespread asian culture is around the world. especially in multicultural cities where people from all over the world choose to live, like singapore, london, los angeles, new york, etc. japan isn't the only asian country that uses chopsticks, and people from chopstick using countries spread chopstick use all around the world too. korea, china, vietnam, etc. and people from those countries also immigrate and have children around world. if you grew up with people around you using something as basic as chopsticks, and you suddenly get complimented for it, it's like complimenting an adult that they can read well in their own language. it feels wrong.
it's a dangerous attitude to think a group of people who are very diverse are all the same. I understand why it is done. It lowers stress, because you don't have to worry about understanding the individual person, and just think they're all a certain way. It is the equivalent of a foreigner going to tokyo, and thinking "all japanese are like this" or "all japan is like this" but all he has experience with is tokyo.