On July 4, 1960, the Eugene (Ore.) Register-Guard rang in Independence Day with a dire Associated Press report by one Norma Gauhn headlined “American Dialects Disappearing.” The problem, according to “speech experts,” was the homogenizing effect of “mass communications, compulsory education, [and] the mobility of restless Americans.” These conformist pressures have only intensified in the half-century since the AP warned “that within four generations virtually all regional U.S. speech differences will be gone.” And so as we enter the predicted twilight of regional American English, it’s no surprise that publications as venerable as the Economist now confirm what our collective...