The incidents underscore a key fact about modern American society: As of 2016, 35 million U.S. citizens over the age of 18, or more than 15 percent of the adult population, speak a language other than English at home, according to the U.S. census.
What's more, the census data show that the link between U.S. citizenship and English language use has been growing steadily weaker over the past few decades. But that's not because newcomers to the country are less likely to be proficient English speakers than their peers in earlier decades. If anything, English proficiency among nonnative speakers is increasing.
Pick seven adult citizens at random from the U.S. population, and the odds are that at least one of them speaks something other than English at home, according to the Census Bureau's American Community Survey.
If you include noncitizen residents, the odds are even higher: 66 million U.S. residents ages 5 and older — 21.6 percent of that population — speak a language other than English at home.
The share of non-English speakers has been rising steadily for more than three decades. U.S. residents today are nearly twice as likely to speak a language other than English at home as residents in 1980, for instance. The census doesn't have as much long-term data on the percent of adult citizens speaking something other than English, but since 2009 it has been rising in tandem with the share of all resident non-English speakers.
The map below shows the distribution of citizen non-English speakers nationwide as of 2016.
Non-English-speaking households tend to be concentrated in the Southwest and in southern Florida, primarily because most of them speak Spanish. But you can find significant proportions of non-English-speaking households in most major metropolitan areas in the United States, including Atlanta, Chicago and the Acela corridor running from D.C. to Boston.
In 39 U.S. counties, a majority of adult citizens speak a language other than English at home. Most of these counties lie along the southwestern edge of Texas, but the largest of them are Bronx County in New York (1.3 million people with more than 53 percent of adult citizens not speaking English) and Miami-Dade County in Florida (2.5 million people with more than two-thirds of adult citizens not speaking English at home).
The Montana Border Patrol agent who questioned the two women at the gas station told them he did so because “you guys are speaking Spanish, which is very unheard of up here.”
Montana is, in fact, one of the states with the lowest percentages of non-English-speaking citizens: As of 2016, 3.3 percent of adult Montana citizens spoke a language other than English at home. Compare that with California, the state with the highest share of non-English-speaking citizens, at more than 35 percent.
But even 3.3 percent is far from unheard of. Pick 30 Montanans at random, and odds are that at least one of them speaks a language other than English at home.
Although the United States doesn't legally mandate an “official” language, English is the de facto language of the land. People who lack English proficiency may face all manner of social, educational and economic roadblocks as they attempt to navigate society.
However, the census data show that more than 60 percent of citizen and noncitizen U.S. residents who speak other languages at home also speak English “very well.” They're bilingual, in other words, and speaking other languages out of choice, not necessity.
What's more, English proficiency among all residents who don't speak English at home has been steadily increasing since 2005, when 55 percent said in a census that they spoke English “very well.” The Pew Research Center has found that this trend is particularly pronounced among American Latinos.
Looking at adult U.S. citizens only, the English proficiency rate among those who speak another language at home is even higher, at 69 percent.
There's a stereotype that people who don't speak English are undocumented immigrants who do so because they lack English language proficiency. But as the census data show, that's not at all the case.