Before WW2 large parts of the country only spoke German, and there were pockets all over that only knew the language of where they immigrated from.
It wasn’t until the World Wars and the advent of radio that everyone started moving to just English.
Hell, the town next to where I grew up still has German street signs and most businesses have their signs in German.
I think a decade or two ago they added English signs as well, but there wasn’t any law that forced them too.
People being mad about this stuff, is just boomers who think history started when they were born and nothing should fundamentally change as long as their alive.
Doesn’t matter if it’s good or bad, they want everything to be exactly like how when they were kids. And by the time they were kids, was the big push for an English only America.