I am not sure about the decision to write laws in German as well as English but I do know that there were areas of the nation that had large German speaking communities. In the Midwest and Pennsylvania many anabaptists immigrated and generally continued speaking both their own dialect and High German which was the language used in church. After World War I began many of these communities began to transition to English. As an example,in Berne Indiana they were not forced to switch but it was a conscious decision because of the pressure. The church began to give one sermon a month in English, starting the transition. I do not know if that is the same situation other communities experienced at the time. World War II was also a factor. The number of children learning German was falling by the 1930s but when the Nazis took power, it fell further. One of the core tenants of the anabaptists in the region was pacifism, and they faced a lot of criticism for both speaking the language of the enemy and for not fighting. In Berne the KKK threatened church members and burned crosses in the yard of the church. There are still some German speaking anabaptists communities like the Old Order Amish, the Hutterites, and some Mennonite communities, but it is not really a community language beyond these groups.

Anecdotally, my grandparents were born to Swiss Mennonite families in Indiana and they did not speak German or attend Mennonite churches but their parents did. My greatgrandfather moved north to Michigan. My father lived with him and they would spend a lot of time at Amish houses, I am assuming because there were similarities with how he grew up. I also know a few older people whose parents did not speak English until they were adults, even though their families had been in the US for generations.