During World War I and World War II, being German-American in the U.S. became less-than-agreeable.  At that time, due to interpersonal and institutionalized discrimination, many German-Americans actively tried to assimilate into a still-very British America by downplaying their ethnic characteristics.  This cartoon, published in 1921, illustrates how German-Americans attempted to do this and how well-aware the larger society was of their efforts:

(I have long since lost the source on this, but if someone sends one in, I will gladly link to it.)