A useful comparison may be to Spanish in the United States today.

As for how widespread this was, some examples at the time included a lynching of a German seeking naturalisation:

> One such death of note was that of Robert Prager, a German seeking naturalization in St. Louis, Missouri who was accused on the night of April 14, 1914, of being a German spy by a mob of 300 "men and boys" after he had allegedly shared words at a socialist meeting earlier that evening. The jail where he had taken refuge from the crowds was quickly overrun and being stripped of his clothes, he was led down Main Street with a rope tied around his neck, and was forced to walk the route, and with shattered glass bottles being thrown down in his walking path, he was forced to sing patriotic songs. He was forced during this walk to kiss an American flag which had been wrapped around him. He was walked to a hanging tree at the edge of town where he was lynched. In an article from The St. Louis Global-Democrat, it was reported that there had been multiple incidences of mobs tarring and feathering individuals.

Note that this was prior to US entry into World War I.

Language bans:

> Language use had also been the primary focus of legislation at state and local levels. Some of these regulations included the publication of charters banning speaking German within city limits. A total ban on the teaching of German in both public and private education could be found in at minimum 14 states including ome states would extend this to ban the teaching of all languages except for english, although the majority who would ban non-english languages typically only banned German. A total ban on teaching German in both public and private schools was imposed for a time in at least 14 states, including California, Indiana,[11] Wisconsin,[12] Ohio, Iowa and Nebraska. California's ban lasted into the mid-1920s. The Supreme Court case in Meyer v. Nebraska ruled in 1923 that these laws were unconstitutional.[13]In October 1918, a bill intended to restrict federal funds towards states that enforced English-only education was created. On April 9, 1919, Nebraska enacted a statute called "An act relating to the teaching of foreign languages in the state of Nebraska," commonly known as the Siman Act. It provided that "No person, individually or as a teacher, shall, in any private, denominational, parochial or public school, teach any subject to any person in any language other than the English language." It forbade foreign instruction to children who had not completed the eighth grade.I n Montana, speaking German was banned in public for two years during World War I.[14] Pennsylvania's legislature passed a German-language ban, but it was vetoed by the governor. Churches during this period such as the Lutheran Church became internally divided over services and religious instruction in German and English.[15]

https://en.wikipedia.org/wiki/German_language_in_the_United_...

In Iowa in particular:

> Harding's proclamation codified four rules for the state. First, Iowa schools - public, parochial and private - could only teach in English. Second, public conversations, including on trains and over the telephone, must be in English. Third, speeches or public addresses could only be given in English. Fourth, churches cannot conduct public worship services in any language other than English. We know this proclamation today as the Babel Proclamation.

https://www.thegazette.com/guest-columnists/a-century-ago-io...