Final answer:
True, the most troublesome religious boundary in Western Europe is indeed in Ireland, specifically Northern Ireland, where historical conflicts between Roman Catholics and Protestants have caused significant tension.
Step-by-step explanation:
The statement that the most troublesome religious boundary in Western Europe is in Ireland is true. The Northern Ireland conflict, often referred to as 'The Troubles,' highlights the deep-rooted religious and nationalistic divisions between Roman Catholics of Irish heritage and the Protestant Christians of Scottish and English descent. While technically part of the United Kingdom, Northern Ireland has experienced significant strife, with issues exacerbated by paramilitary groups such as the Irish Republican Army (IRA).
History has shown that the island of Ireland has seen recurring cycles of conflict and attempts at peace. The deeply entrenched religious differences in this region have also been influenced by political motives, akin to other historical confrontations such as the Protestant Reformation and the combatants in the Reconquista on the Iberian Peninsula.
Today, centripetal forces and the potential for social unity strive to mend the historical divide, but the consequences of these religious and nationalist tensions still linger in Ireland, as they do across many parts of Europe where immigration and cultural changes challenge traditional religious homogeneity.