My grandparents immigrated here from Poland in 1914. They made sure that their children spoke English. While her older siblings spoke two languages, my mother was born in 1926 and she only spoke English as did her younger sister. They assimilated! Ditto with my Italian grandfather. My dad only knew the Italian cuss words.
I have no patience with people who come here and refuse to teach their children English. They should be deported and they should receive no government assistance. Before you know it English won’t be a requirement for citizenship!
My ancestors came here from Switzerland in 1854. As recently as say 1950, my grand mother and her sisters and other Swiss of their generation and church spoke French at home.
I was exposed to the French but there was no attempt to even encourage me at all to learn French. My mother understood but never spoke. Her sisters never learned any French at all.