There's always more than can be said about his specific name and family history, but I wrote an answer on the German immigrant experience in schools that gets at some of what you're asking. The full answer is here but the part I think might be most relevant for your question is about the shifting nature of whiteness in America and geographical differences:

It should be said World War I, and tensions before the war, negatively impacted the dynamic between German Americans and their neighbors. Indiana and Texas, for example, had been a welcome place for German immigrants, including mandated German instruction in most Indiana high schools as a way to explicitly draw German immigrants to the state. (Basically, they were saying, "your child will do well in at least one class in school and we're cool with them speaking German." In 1900, more than 200 American public schools in more than a dozen states used this approach to appeal to German immigrants.) Steps, though, by xenophobic Americans brought a swift halt to German language and cultural education. Many of the men advocating for an end to anything and everything German in schools were engaged in what can best be described as "superpatriotism." They saw it as their responsibility to rid their schools of any vestiges of the enemy, even though they had lived side by side with German immigrants for generations. But again, it was location dependant; New York State offered German language high school courses and corresponding exit exams until well into the modern era.

Generally speaking, the pushback against Prussia in American schools during and after World War I was a general prejudice against all things German. A great deal of this was tied up in how white Americans have set and shifted the boundaries around who counted as white. That is, German Americans weren't kicked out of the tent of whiteness - German speaking children were still allowed to attend public schools and German speaking adults were paid the same as other workers, whereas Black Americans were still barred from schools and paid less. So, while a German immigrant in the 1920's and 1930's may have felt the impact of nativism and xenophobia and elected to minimize the things that would draw attention, it would have been a matter of choice. The sentiment of the xenophobia would shift from German culture in general to German American children in specific by World War II. As an example, the topic of "disordered" thinking of American children raised in households speaking in German was a popular topic for dissertations well into the 1950's.

I'm also going to leave a link here to a question about the "Americanization" process for immigrants, including some history about the (not exactly accurate) idea immigrants were forced to change or Americanize their name when arriving at Ellis Island or other immigration points.