Well, Indi, you nailed it again. But this time, I think you got underneath the skin on our faces. Our "Speak English" only mantra sounds like a command, but it is not.
It is a symptom of our hidden fears. The fear that I am not smart enough to learn another language. The fear that people can talk about me, right in front of me, and I won't know what they are saying. The fear that people will laugh at me if I don't pronounce words properly. The fear that I will accidentally use the wrong word and get myself beat up, or fired. The fear that all my fancy things, titles and degrees will not be enough to make me important if America suddenly decided every school kid has to learn a second language. The fear that my peers, even my own family, will think, that I think I'm better than they are because I speak another language. The fear that someone will think I'm an alien, a spy, a traitor or an uppity-elitist because I speak another language. The fear that learning another language will make me an outcast in my country.
Most all of our deeply defended cultural "norms" hide similar fears. From the outside America looks strong, but inside every American is a chicken. Most of us are just tending our roost, laying our eggs, and hoping the man doesn't take all of them.
The biggest chickens run around with guns trying to run the chicken house. Some of our biggest chickens wear fancy feathered suits with big name tags on their scrawny chests and do their best to strut their stuff and crow about it. Cock-a-doodle-do - doesn't have a doodle and never does.