The religious map of Europe has changed remarkably little since the Reformation. To a large extent, the confessional allegiances of European states today reflect the principle of cuius regio eius religio ("whose realm, his religion," meaning that a nation's ruler gets to decide its religion) established by the Peace of Augsburg in 1555. In order to bring an end to the destructive, bitter conflicts unleashed by the Reformation, it became necessary to allow the rulers of each territory to determine which religion their subjects should follow.
Catholicism remains the denomination of the vast majority of Italians, which isn't surprising given that Rome is the spiritual heart of the Roman Catholic religion. Though a strongly secular state, most Christians in France are Catholic, as indeed are those over the border in Spain as well as their neighbors in Portugal. Germany is a mainly a Protestant country, largely on account of its leading role in the Reformation. However, large swathes of the country, mainly in the South and West, are strongly Catholic, especially Bavaria. Over the Southern German border, Austria is also a Catholic country. Switzerland, the birthplace of the Swiss Reformed Church, is relatively mixed in terms of religious observance, though officially there are more Catholics than Protestants.
Croatia is Catholic, in contrast to its Orthodox neighbors in Serbia. Northern Europe is predominantly Protestant, but the Republic of Ireland is overwhelmingly Catholic, as are Belgium, Luxembourg and the micro-state of Lichtenstein. Many of the countries of the old Eastern Bloc are either Catholic or have large Catholic populations. These include the Czech Republic, Slovakia, Hungary, and Lithuania.