When I try to explain to my students, both in America and when I was overseas, the allure of what it meant to be "American," I'd refer to the Germans from Russia. Their exodus from Russia was on a massive scale, and it wasn't just the Volga German-Russians as there were also Black Sea German-Russians who mostly settled farther south, and also a large contingent of German-Russians who emigrated from what is now Poland but was then under Russian control. My father has one branch of the family from Volga German-Russians and one branch from German-Russians in what is now Poland.
They lived in Russia for nearly two centuries without changing their language (when they went back to Germany, the local German dialects had evolved so much that they could barely understand each other), their religion (Protestant), or their culture for the most part. When the Czar all but chased them out, he was forcing them to be baptized into the Russian Orthodox Church, speak and learn Russian in school, and serve in the Russian Army. They fled that to settle all across the Great Plains in the U.S. and Canada, and within one generation they had started speaking English, had branched out into various sects of Protestantism, were serving in the U.S. Army, and were intermarrying with their American neighbors of all ethnicities. I can't think of another example quite like it in all of human history that wasn't forced at gun or spear or sword point.
When a culture feels threatened, they dig in and stop changing; when they feel at peace and secure, they adapt to whatever is happening around them. Twenty-five years on the Great Plains to a complete makeover of people who had refused to evolve for nearly 200 years in Russia.
P.S.--Different regions of Russia represented different eras of migration from Germany. The Volga Germans were probably the earliest migration, and they were brought in by Peter the Great shortly after conquering that territory in the hopes that they'd speed up the agricultural production and technology of the locals before eventually blending into the community. Likewise, Catherine the Great did the same with the Black Sea region of Russia (what is now Ukraine) about 70 years later. The Germans under Russian rule along the Baltic Sea (what is now Poland and the Baltic States) were the descendants of earlier German merchants from the Hanseatic League who had spread out all over the Baltic to trade in the Middle Ages and Renaissance periods.