The Rusyns never had a state of their own.
The region is probably about the size of Switzerland (give or take), but it has always been controled by others, and is currently divided between several states.
Pope John Paul II had stated that his mother was a “Rusin”, but that is often taken to mean Ukrainian (especially by Ukrainians). She may have been a Lemko (one of the Rusyn tribes of southern Poland), but I don’t know anyone who can state that with total conviction.
The area the Rusyns live in was once a mountainous eastern frontier of the
Moravian empire. A strong case can be made for the Rusyns receiving Christianity from the missions to Moravia by SS Cyril and Methodios and I believe they feel the brothers passed through their homeland. The Rusyns probably suffered terribly when the Magyars blew through into the Hungarian plain but most likely had not been subjugated by the Scandinavian Rus who ranged up the
rivers (and eventually founded the Kievan state). The Ukrainians trace their own conversion to the baptism of Grand Duke Volodymyr of Kiev about one hundred years later (988AD).
Both groups then, were converted into the same liturgical, theological, spiritual tradition, but from different directions and at different times. It seems (not sure about this) as though the Orthodox Rusyn-Ruthenians received their bishops through Romania and had Constantinople as their Patriarch, while the Orthodox Ukrainians received their bishops from Kiev while having had Constantinople as their Patriarch.
Liturgically, there are slight differences in local practice (to be expected). The Ruthenians have a strong tradition of congregational chant (although it seems to have taken hold less than 150 years ago, before which the cantor sang alone), and in the villages the two principal ministers would be the priest and the cantor. The Ukrainians have their own style of chant and I cannot comment on the rest, except to say that I think they have a much stronger choir tradition. (Also, Ukraine is a pretty big country comparatively speaking, so it is hard to generalize.)
I have noticed (when visiting) that the Rusyn-Ruthenian parishes almost always have a tetrapod before the Ambo, the Ukrainian parishes usually do not. Both use iconostasis. Otherwise there is not much to say about the interior spaces of the temples.
As to the history of these two groups in coming to the USA (their challenges and conflicts), you may wish to read
Clash of the Titans. As I recall it is pretty informative.