From the era of Napoleon through World War II, how has the development of Europe changed due to imperialistic desires and nationalism?

Their ideas got worse but they still continued to grow in strength. For example, Nazism is an idea that never should have existed in the first place, but even during this time with Hitler leading everyone, Europe rose to power quite quickly especially after just coming out of World War I where the Treaty of Versailles left Europe with pennies. While Hitler was an absolute fool, he definitely knew how to bring Europe out of its very own Great Depression. Later joining the United Nations and siding with America against Communism, Europe has changed a lot since then. As of today, it seems like they have made a full recovery but it's important to make sure past events never occur again.