I don’t think so but I have some idea. I was kinda uncomfortable with people from country when I was abroad, mostly because the fact your nationality is the same doesn’t mean you would get along or have the same vision about things or even feel closer to them about your country matters (especially for those living abroad since they were little).
Koreans tend to be overly friendly while as americans are more reserved. Also for the fact he obviously is more used to speaking english than korean. Combine that with his brother being well known around the university, especially with Koreans, he wants to avoid unnecessary korean dialogue.
By experience, I'm brazilian, and when abroad brazilians tend to flock together and don't even try to you know, blend, try different... Same happens with other cultures. And Taehee has another problem to add, his annoying brother.
Do we know why he’s uncomfortable with Koreans ?