I don’t think many Americans identify as German-American. However 10% claiming German ancestry sounds plausible.
Texas, where I live has too many towns founded by German settlers to list. But here’s a few: Schulenburg, Muenster, New Braunfels, Warburg, Weimar, Bulverde, Boerne, Brenham etc.
There aren’t many German speakers left, but they still have lots of pride in the foods, music, culture and German surnames are quite common.
The one I remember had mercury acting as a recoil dampener. No idea if they actually work.