For Texas Germans, some of A, some of B. Churches in central Texas towns with significant German-speaking populations commonly worshiped in German, and those towns had German-language newspapers up through the 1920s and 30s. The drop-off appears to have started around World War 1, and was pretty much complete by WW2. Some of my high school classmates (born ca. 1980) had German and/or Czech-speaking grandparents who grew up in the 20s and 30s, but tried raising their children as English speakers. Result: my classmates' parents could always understand Oma and Opa, but their grandchildren couldn’t, which was part of why German was an unusually popular foreign language option at my high school (the excellence of the long-time German teacher was the rest).