While not quite answering your question, leading up to and during WWI a substantial population of Germans had recently migrated to the Midwestern US states. In fact, Germans were the largest non-English speaking minority in the US. The 1910 US Census counter 8 million First and second generation German-Americans. Church services would be held in German or the immigrants languages, street signs be made in German and kept traditional German surnames. Kindergarten is a German tradition that was imported with this group. But after the breakout of WWI the local governments all the up to the top began to crack down on what was perceived as a possible dangerous minority. So the suppression of German culture and language in day to day life was put in to effect. Schools in the Midwest that used to give lectures and instruction in German changed their policies, newspapers stopped printing in German, and religious ceremonies would have the “Language of Luther” discontinued or at least bilingual. Street names changed, he’ll even names would be Anglicized. (Read also Royal Family of England) So before WWII the massive German population had been Anglicized... or rather Americanized.

US Census Department (1910)

Moothart O'Bannon, Cynthia. "WWI altered the German accent of Allen County". fortwayne.com.

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