Well, for what it’s worth perhaps I can provide a little insight. I grew up in ROCOR (Russian Orthodox Church Outside Russia) and know that Church very well. My wife and I (she doesn’t understand Russian or Slavonic) later attended an English-language OCA parish. (ROCOR does have some English-language parishes, but my home parish was not among them.) To her it was far more comfortable a fit. To me the pews were odd (the wonderful priest was very touchy about defending them in a very endearing sort of way).
Other than that, I was totally okay with it, and my son was baptized in the OCA.
Please excuse the really too broad history review (more info is readily available online), but the OCA does not consider itself to have grown out of ROCOR (and while ROCOR interprets the history a bit differently, I think they too would view the groups as splitting, not necessarily as growing out of one another), although there was overlap early on. The OCA sees itself as the successor to the original Orthodox missions in Alaska in the 18th century. Interestingly, although the OCA was often accused by ROCOR as being too close to Moscow during the Soviet period, it obtained autocephaly in 1970, while ROCOR came back into communion with the Patriarch of Moscow in 2007 (not everyone in ROCOR agreed with this, an several groups since have splintered off).
The whole American situation was and still is very irregular, though thre are signs that this is changing, thankfully. Before the Russian Revolution, as far as I know all Orthodox in America, regardless of their ethnicity, were under the Russian archbishop, who was for a time St. Tikhon (later Patriarch of Moscow). After the Bolshevik seizure of power, chaos ensued and the American situation (as well as communication with Moscow) became problematic as the Church in Russia was actively being persecuted. At this point many of the ethnic home Churches stepped in to set up hierarchical structures for their co-ethnics because no one quite knew what was going on. Keep in mind in the nascent Soviet Union you had the Bolshevik sponsored heretical “Renovationist” Church claiming to be the legitimate Church (never seen that way by the masses and died off by the early 1940s), you still had the ROC as a persecuted shadow of its former self, and you also had priests and bishops going “underground” and forming the Catacomb church to preserve the faith. Abroad, meanwhile, you had the Karlovsky Synod (the Church in Exile or ROCOR) abroad breaking from Moscow (with the blessing of Patriarch Tikhon, according to ROCOR), along with other splits (e.g., in France).
Okay, that’s probably more than OP wanted to know (and hasn’t even scratched the surface of the sad history, the divisions of which are directly due to what happened in 1917).
Is the OCA ethnic? Not really any longer, in my experience. Of course, this will vary depending where you are. And it’s head, Metropolitan Jonah, is an American convert (former Episcopalian). In any case, the OCA was always more Rusyn than Russian. Very many Ukrainians, people from the former Austro-Hungarian Empire, etc. And quite a few families that have been in America for multiple generations. Most of the “ethnics” I’ve met in these parishes are about as American as they come.
It is also probably, along with Antioch, the largest convert magnet in American Orthodoxy, I think precisely because it is far less ethnic than ROCOR or similar groups. And yes, I would say ROCOR was more “traditional” in the sense of preserving the forms of devotional life as they existed in Russia before the Revolution, but I would never say one or the other is more “orthodox.”
For what its worth…
