This
bumper sticker, seen most often in
Texas and the
Southwest US, is a reminder of the linguistic history of the
United States.
Much of the Southwestern US was once part of Mexico. The people who lived there were Mexican. So it's no surprise that they spoke Spanish (and possibly a local language too). Then came the Mexican-American War, after which huge expanses of recently Mexican land had become American.
Official English advocacy puzzles the people whose families have pretty much always lived in the area. Speakers of Spanish are being told that if they didn't want to speak English, they shouldn't have crossed the border. Their response is often something like We didn't cross the border; the border crossed us.
I see the same thing in Florida, where Yankee migrant loafers come down for the winter and grumble about the presence of Spanish and Haitian Creole in Miami. The ironic bit is that Florida has been Spanish-speaking for more of the last 500 years than it has been English-speaking.
Those who say "Welcome to America, now learn the language" have every right to express that opinion. I just wish that for once I could hear someone say it in Seminole, or Cherokee, or Lakota...