The Laskan Orthodox Church
The primary church of the Laskans is, surprisingly, the Orthodox Church. The Orthodox Church always hadan unusally large following in Alaska, a tradition dating all the way back to its colonial Russian past. When the world began regressing, the Orthodox church was prepared: after all, the entire organizational and liturgical structure of the Church came about during the Middle Ages, as opposed to those pussy post-Renaissance Protestants. Using its organized network across Laska, the different Orthodox churches coordinated their efforts, and worked to ensure their hegemony over the whole of the land. The local Catholic Churches quickly reconciled, ending the schism, but most of the Protestant churches were slower to do so. From Joono, the center of the Orthodox church, they either convinced them, forced them, or got a friendly local leader to burn them down. Eventually, thanks primarily to the conversion of most of the leaders of the first Great Raid, Orthodoxy was the number one religion in Laska.
As it turned out, Orthodoxy lent itself quite well to the slowly developing folklore of polytheism and ancestor-worship. Orthodox icons, considered holy and said to be capable of working miracles, were already halfway to being idols. As Laskans began building totems and fetishes and idols themselves, many were simply called "Icons", blessed by the local priest, and they were free to sacrifice chickens to it.
The Orthodox Church also ministers quite extensively in the wastes beyond Laska, among the Athabaskans and Inuit of Eskimoland. The common folk generally consider them heretics, unfaithful devil-worshipers that only put on the trappings of faith when, ironically, the average "Eskimo" is far more true to the Church's teachings than the average Laskan. While the Eskimos are perhaps more open about the non-traditional aspects of their Orthodoxy, which does incorporate a lot of Native beliefs, they are still generally more faithful.
The Church is loosely organized, but is theoretically governed by the Laskan Patriarch in the Joono St. Nicholas Cathedral, which has been vastly expanded from its original pre-Regression form. The Church moved to Joono as the Regression began, hoping that by moving to the state capital, it would be easier to spread their control across the state. It is difficult for the Patriarch to issue direct control over most of his priests, since they are often located in isolated locales, giving local priests a good degree of leeway that they have certainly taken advantage of.
The Holy Church of St. Nicholas as it stands today
Generally, Orthodoxy is not too hostile towards other religion. This is in part due to necessity- after all, they don't just have their own pagan populace to deal with: trade with the Buddhists of the Pacific Northwest and the Scientologists of California is one of the only things keeping them afloat. Buddhism has even made inroads, especially on Graham Island and the city-state of Kechikan, with smaller colonies spread throughout the Alzandar Archipelago. Though these converts and colonials have been excommunicated by the Orthodox Church, they still consider themselves Christian, seeing Buddhism as an addition, not a subtraction.
The Church has been getting less and less strict about canonization, with most of the heroes of Laskan history being accepted in. There have been several periods of iconoclasty, when the church (mainly in Joono, which is the center of the church and home to the the Laskan Patriarch) has tried to crack down on the "folk-saints", superstitions and idolatry, but this is always met with hostility by the common folk of Laska. Only time will tell how far the Orthodox Church will allow the Laskan people to fall into the pit of polytheism and sin- will it go down with them, a slave to cultural and economic reality, or attempt a glorious crusade upon the Laskan people?