But now on another board some guy keeps telling me Protestants are closer to Catholics because their views on civilization are more similar.
He is almost certainly referring to a theory proposed by Samuel P. Huntington in
The Clash of Civilizations and the Remaking of World Order (New York: Simon & Schuster, 1996). You have to understand that Huntington was concerned with the field of international relations, not with theology. Huntington proposes that Europe is divided between two civilisations, western civilisation and Orthodox civilisation. He argues that western civilisation is coterminous with what was once western Christendom, which from the 16th century became the region of Europe in which Catholicism and Protestantism were the main denominations of Christianity. Despite the Reformation, countries such as Britain and Poland continue to belong to the same western civilisation because they share a common intellectual history.
You have to remember that Huntington was writing only five or six years after the end of the Cold War. Part of the purpose of his book was therefore to establish the case that countries such as Lithuania, Poland, the Czech Republic, Slovakia, Hungary, Slovenia, and Croatia (and, perhaps more contentiously, Estonia and Latvia) belong firmly within the domain of western civilisation rather than within the domain of Orthodox civilisation dominated by Russia.
Closely related to Huntington’s conception of western civilisation is the idea of central Europe. For about 45 years between the end of the Second World War and the end of the Cold War, Europe was divided into western and eastern Europe. Western Europe included those free, democratic countries with capitalist economies, while eastern Europe included those countries existing under communist regimes. This division of Europe into a western half and an eastern half was, however, only a brief aberration in the longer history of the continent. Before 1945, countries such as those enumerated above were considered to be part of central Europe, a region of Europe that also included Germany and Austria (and arguably also Switzerland and Liechtenstein). Since the end of the Cold War, countries in east-central Europe have made conscious efforts to resist the term “eastern Europe” and argue for their central European identity.
Since this is a Catholic forum, it is worth noting that Huntington identified Ukraine as a country that is divided between two civilisations, the western half of Ukraine, which is predominantly Catholic, belonging to the western civilisation, and the eastern half, which is predominantly Orthodox, belonging to the Orthodox civilisation.
It is also worth mentioning a related theory proposed by Patrick Leigh Fermor, which argues that the modern Greek state has always struggled to reconcile the Hellenic and Byzantine aspects of Greek history. The Hellenic aspects (those deriving from ancient Greek culture) place Greece within the domain of the West, while the Byzantine aspects (those deriving from the later, Christian Roman Empire) place Greece within the domain of the East.