I’m sure around 1900 the number was likely higher.
The thing is that those people worked to actually learn the language out of pride and a desire to be American, and their kids were required at home and at school to master it.
The number of people refusing to assimilate?
My Great-Grandparents came here from Italy around 1900. All them were speaking English very quickly. They would not even teach us Italian when we were young because we were American. My father’s ancestors came here in 1633. I think we knew the language. My home city of Malden MA is now 24% Non-Citizens.