I work for a japanese company and since we are in US, about half is japanese and half is non-japanese. I've heard some Americans have complaints here and I had a chance to hear it on my own yesterday.
It just so happened that Japanese workers tend to get together on their own and they don't invite non-Japanese. For example, they all go out together to eat/drink; or someone has a private party and all Japanese are invited but not non-Japanese. Americans are not so happy about being excluded.
One American worker asked one Japanese worker why they were not invited, and this Japanese person answered it wrong. She explained that the company was not paying for a dinner; she was paying for herself. It sounded like Americans are cheap, equals they cannot afford paying for a dinner/drink so that's why they are not invited.
That is not the actual reason! I heard once from my boss (japanese) why they don't go out with Americans. It's because of the language. He told me he cannot have a good relaxing time if he had to speak English. Japanese workers (most of them) do not want to be forced to speak English outside of the office!!
I kinda understand that. For me, it was my decision to come to this country; but for most of japanese people working here, they were sent by the parent company. So they were forced to study/speak English... I can see why they do not want to use their head while having a good time eating/drinking...
But I also understand that we should not exclude Americans when having a party. That's discrimination!
So I come between those two groups. I am not on either side actually. But I hope that I can give American people a good reason why they were not invited... I'm not sure how much they understand how difficult for foreigners to communicate with language other than their own...