In many ways it depends on which part of Europe you are asking about. It de-centralized some "empire" like structures including the break up of the Austrio-Hungarian empire and led to many of the effects that would see other European countries losing their colonies (though the real effect there wasn't necessarily felt until after WWII).
The revolution in Russia leading to the eventual rise of the Soviet Union was helped in many ways by the devestation, hunger and economic collapse throughout Russia after the war (along with the purge of most of the army officers), perhaps worsened the outbreak of the flu that killed millions thanks to malnutrition and lack of nutrition throughout the continent.
Many people also point to what they call the "lost generation" given that most of an entire generation of young men from Europe died in the war and those who witnessed it never recovered from the aftermath. There was an increase in efforts to bridge national borders since many felt that nationalism led to much of the causes of the war. There was also a great growth in philosophies like nihilism since people saw so much destruction and had no faith in humans afterwards.