In 1914, all of Middle and Eastern Europe was governed according to constitutions (in the English sense) that were explicitly Christian. The King of Prussia (and German Kaiser) was Calvinist, the King of Württemberg was Lutheran. The Emperor of Austria-Hungary, the Kings of Bavaria and Saxony were Catholic. And, of course, the Tsar was Orthodox. By 1918, all of these constitutions had vanished and were replaced by explicitly secular governments. Admittedly, there continued to be Christian monarchies in several of the smaller states, but once the German/Austro-Hungarian/Russian governmments traded their Christianity for secularism it was as if the torso of Christendom had disappeared, leaving only the extremities. The mantle of Western European leadership was promptly taken up (temporarily) by the anti-clerical, secularist French, and the pragmatic English, succeeded briefly by the even more anti-Christian Nazis, and eventually superceded by the influence of the arch-secular U.S. And, through all that time, Russia was enslaved by a brutal anti-Christian tyranny unparalleled in history.
Modern European political philosophy is now based on Rousseau rather that Scripture and Tradition.
Which, IMO, precisely explains Western Civilization's current descent into savagery -though a savagery about which there is nothing noble.