I agree that if a therapist can be helpful, to continue bringing this up with a good one.
I also wanted to mention that, depending on what your feelings center on, it might not be a bad thing to dislike certain aspects of a particular culture while, in order to gain balance, appreciating what is good.
For example, if you dislike, say, the fact that the Japanese are expected culturally to work totally unreasonable amounts of overtime while never being able to afford a home despite all that overtime? Well, that’s hardly unreasonable! Ditto a dislike of the culture associated with a lot of the adult manga. Or, from a taste perspective, maybe sushi or ramen isn’t your thing. Also totally fine!
If, on the other hand, you have an immediate, visceral “I hate everything about this person and their country” response to seeing a Japanese person walk past you on the street, well, that is a problem, and I recommend you take it to both a therapist and Christ in adoration. FWIW, I have a similar reaction to a particular political/social/religious movement that I spent a lot of time in, to the point that I immediately think horrible things about someone if I find out that they’re a part of this group. I know intellectually that that isn’t fair and that there are a lot of good people in that group, but my experiences with it were such that I still react that way emotionally. Well, emotions aren’t a sin, unless you encourage bad ones, so I try to take the hurt, pain, and anger that I feel at that group to Jesus and say “this is less about them than about me. I’m hurting a lot right now because of those experiences, and I’m reacting unreasonably to Person’s Name. Help me to react with kindness and love instead.”