The boundaries of nationality and ethnicity

Anyone who has observed the behaviour of international students at university will have noticed and probably made a remark about how they stick to “their own kind”. You see the Chinese students all eating together at lunch, in your Tuesday morning lecture the back row is full of Italians, on the way home you walk behind a group of Turkish students. We always say, me and my friends, that they should branch out and mix with other people. They are here to receive a cultural experience, not to hang on to their own.
I know that this is very judgemental of us. I now understand how comforting it is to hang on close to those people and things that are familiar to you. Nonetheless I pride myself in the diverse group of friends I have accumulated here in Marburg. I have friends from Taiwan, Japan, South Korea, Italy, England and America. I thoroughly enjoy the mix of familiar and new, however having such a diverse group of friends has been leading me to feeling a little left out lately. Although I take this as a complement, I am really one of a few, and in some cases the only, “westerner” who hangs out with the Asian students. They spend a lot of time together, they cook together, shop together, travel together, and although I get invited every now and then, there are a lot of things with I do not get invited to. I guess it is understandable. When all the Japanese students are together having a meal, for example, they can easily communicate in Japanese, but if I’m there, then it is all a little more effort because they either need to speak German or translate for me. Even so, sometimes I feel like I’m not really part of their group. I’m just a good friend. If that makes sense?
I find that my “diverse group of friends” and my like for splitting my time between the groups has a toll on my relationship with the English students. Sometimes I miss out on a lot of fun things with them, and I get a little depressed at all of their inside jokes that I missed out on. 
I’m not trying to make this into a sob story. Really I love all of my friends, and I do spend a lot of time with them. I just wish that I could spend a bit more time with some of them. But as my mum says, you shouldn’t wait around for an invitation, you should just invite them. :)