I think that the ethnic jurisdictions can be deceptive, even in churches where the service is mostly or entirely done in another language. What I have found really is that most Orthodox churches are much more international than their jurisdictional names would imply, and much more international than the average American church (I can't speak for other countries). For example, I was had a lovely conversation with an elderly woman in French at a church where the liturgy was entirely in Slavonic, and she in turn was originally from Germany, not France but her husband was French and she didn't speak English so well. While it is true that certain ethnic groups clump together, I think this is more because people like what is familiar whenever possible, not out of any hatred or distrust of other ethnic groups (which is what the words racism or segregated imply). In general, it seems Greeks and Arabs will stick together, and then the East Europeans will stick together, when possible...But then you find all sorts of other cultures in each because most of the countries that these churches originated in have had a turbulent history in the past century, thus creating large diaspora communities, which then will later move elsewhere. So, you have French, German, Spanish, and Portuguese speaking Orthodox of Russian or Syrian or whatever descent in a church in America, but you wouldn't really know they have that other culture unless you took the time to get to know them.
On the other hand, it is true oftentimes that Orthodox hold grudges. With Turkey, this is bitterness amongst the Greeks over the conquering of Byzantium in 1453 by the Turks, the subjugation of the Greek people to the Turks for hundreds of years (including murders, tortures, enslavements, suppression of their culture, etc). Then just in this past century, the Turks murdered millions of Greeks (along with millions of other Christians such as Assyrians and Armenians) as an act of ethnic cleansing, and then kicked the rest of the ethnic Greeks out of Turkey, despite the fact that that had been their home long before the Turks had come along. Today there are only a few thousand Greeks in Turkey, whereas just about 70 years ago or so it was several million. Orthodox people, in general, are very conscious of their history, for better or for worse.