Affected Europe as a whole?
There was a great shift in population. Not only did Europe lose a large number of its men to war, but they lost a very large percentage of their Jewish population to the Holocaust. Not only that, but many Jews immigrated following the war. Elie Wiesel talks (in his later books) about how the Jews were looked down upon as a burden to society in European countries following the war—most notably France where he lived before coming to the United States.
With cultural differences, I imagine that various cultures were affected by the war (and the Holocaust) very differently. The end of World War II established boundaries (and spheres of influence) that determined future political and economic systems for those regions.
It might be easier to limit your topic to two group talked about in the novels—Jews and Croatians. Croatia has had its own issues with ethnic cleansing. Not having read the book, I don't know how much the author explores those issues. As Croatia seeks admittance into the EU, Croatians are experiencing discrimination from Europeans who believe that Croats will bring them down. Croatia wasn't a democracy until the early 1990s . . .
Again, not having read the book, I don't know what the main points were or how they relate to Night.
Eric Noto