Dogface, settle down. I don’t think MC is being malicious, but rather is relying on bad sources.
The site MC linked to seems to make little to no distinction between at least three separate (big C) Churches: the Eastern Orthodox, the Oriental or non-Chalcedonian Orthodox, and the Assyrian / Nestorian Church of the East. To an uninformed Western observer, the differences between these Churches may seem rather nebulous, but they are nevertheless quite distinct, with separate rites, communions, Christologies, etc.
The Eastern Orthodox Church, of which Dogface and myself are members, is quite definitely one single church, with national hierarchies. Although reference is made to the Church of Greece, the Church of Russia, etc., a more accurate rending would be the Church in Greece, Russian, etc., or the Greek/Russian Church, as in the portion of the Church that is made up of Greeks, Russians, Georgians, Serbs, or whatever. With the exception of the Old Believers and a very few Western rite parishes, the entire Eastern Orthodox Church follows the Byzantine rite. The whole Church has a common reckoning for Easter, has a common musical heritage derived from the eight tones of the Greeks, etc. Until the 1920s, all Eastern Orthodox followed the Julian calendar. The Eastern Orthodox Church is quite definitely One Church.
A better case can be made for the Oriental Orthodox communion being less one church and more a confederation of national Churches, in a way that the Eastern Orthodox are not. The Ethiopians, Copts, Syrians, and Armenians all have quite separate liturgies, rites, musical systems, histories, and even different canons of the Bible. Rather than being one Church with national hierarchies as the Eastern Orthodox are, the Oriental Orthodox are 6 national Churches united by a common rejection of Chalcedon.
With regards to parallel hierarchies, there are two main areas where this takes place: the Middle East, where the Catholics, Eastern Orthodox, all of the Oriental Orthodox Churches, Assyrians, etc. have their own bishops, and the New World, where the Orthodox are organized along ethnic rather than regional boundaries, due to the historical circumstances of immigration.
I have never heard of the Greeks and the Russians having different reckonings of Easter, so I will join Dogface in asking for a cite, preferably from a scholarly or Orthodox source.
Disclaimer: the above is solely based on my own knowledge, and I do not claim to speak for any church. I am a layman in the Russian Church Abroad, under the omophor of His Grace Bishop Gabriel of Eastern America and New York.