The Republic of Ireland has historically been Roman Catholic, and indeed, Ireland was the based from which a lot of the Christianization of Europe originated after the fall of the Roman Empire. Roman Catholicism is part of the national identity as it was an institution that help sustained resistance to the Protestants from the United Kingdom after hundreds of years. Naturally, then, it is unsurprising that Ireland has been slow to embrace the institution of divorce that was the defining reason for the establishment of a Church of England separate from the Roman Catholic church.
The 2009 film Ondine set in contemporary County Cork, however, shows the limitations of an ideological commitment not so much to marriage as to non-divorce. Annie, a young girl with kidney failure who binds the central characters in the film, has a mother and father (both alcoholics) who cohabited, but never married, and then split up. While they are certainly not viewed as community role models, their arrangement doesn't leave them ostracized either and they get along much like a typical divorce couple in the United States.
The fact that Annie's mother has a live in boyfriend now who is married with children back in Scotland, also barely makes a stir, while the father's cohabitation with a beautiful woman out of nowhere is notable because a loser guy has found a beautiful woman, not because of the scandal that he is shaking up. Even the father's confessional priest (who is admittedly something of a comic foil) doesn't even seriously hope to make the father feel guilty about "living in sin" with her.
The film is obviously just a feel good magic twinged romance and not intended to be a hard hitting documentary of attitudes about marriage in Ireland, but I think that it is fair to say that Ireland's discomfort with divorce as a lived reality is profoundly different from Japan, for instance, where out of wedlock parenting is more rare than anyplace else in the world, and divorce is legal but quite rare.
The cultural package of modern Western culture is intertwined enough, that even if you reject some rather important part of the package, like the institution of divorce, except in comparatively rare cases, it is hard not to find imperfect work arounds that are similar in effect, if not form. Serial monogamy is a much more core part of the Western cultural package than specific rules relating to marriage and divorce that implement that culture.