The most often used German townsname in the US seems to be Hanover/Hannover - which is interesting, as it is a rather mid-sized city of half a million. Though the reason for this is most likely that it's also the name of the duchy and later kingdom of Hanover which was in a personal union with England from 1714 to 1837. Apparently, quite a number of soldiers from the state of Hanover (see https://en.wikipedia.org/wiki/Germans_in_the_American_Revolu...) were sent to the US to fight against the American revolutionaries - some of them probably stayed on and founded these cities. Well, obviously much more complex, but might be one reason for the higher than expected number of towns named Han(n)over in the US.

Similarly there are a lot of US towns named Lafayette, Fayette, or Fayetteville, after the marquis de Lafayette, who fought for the US in the American Revolution.

Also interesting here is a common American use of the place name La Grange/Lagrange being a reference to Lafeyette's home castle (as opposed to the mathematician from whom we get such concepts as Lagrange Points).