I'd be interesting to see what the percentage was 100 years ago.
I remember a long time ago reading an article about the Irish immigrants in the late 1800s and it was a big deal that almost half spoke Gaelic instead of English. They even had Gaelic newspapers published all over the North East.
This was also a major political issue at the turn of the century with so many opposing Chinese immigration and so few speaking English.
I suspect, if we had time for a deep dive, the language trends were far more diverse then. Politicians like to use it as a culture wedge now, but historically we probably are far more homogeneous now than we were 100 years ago.
One of the big things mentioned at the Ellis Island museum is how few immigrants spoke English and they weren't required to. The immigration questions were translated into about 40 different languages.