Is it true that many Americans have German ancestry? And is that something that affects Americans, like do they talk about it etc.?

I'm from Germany and after noticing that many American personalities have German backgrounds I recently looked up that apparently German is the biggest ethnic group in America and that like 12% of all Americans have German ancestry so basically more than 1 out of every 10 people.

I knew that there are some people in America with German ancestry but I never thought it's that many. I always thought that there were other way more common ethnic groups such as UK, Irish or something Asian/African and thought Germans are a minority. I never thought that Germans are so prevalent in America though and that they're actually the biggest ethnic group. I wonder if that is a topic in American conversation cause I assume many Americans are curious about their ancestry and many might even have had contact to family members that are directly from Germany. And I wonder if they identify as American or German or both? (For example I always hear "African-American" being used but I'm not sure that I heard "European-American" that often)