Source: The long adios
From this article: "Linguists have often referred to America as a “language graveyard”. Despite being a country of immigrants, it has tended to snuff out foreign languages within two or three generations. Spanish might be different. Hispanics account for 18% of America’s population and are projected to make up 28% by 2060, according to the United States Census Bureau. Given the large size and rapid growth of the Hispanic population, some people used to fear that Spanish would not only endure but overtake English, especially in states like California and New Mexico, where Latinos are the largest ethnic group. That concern has turned out to be unfounded. Between 2006 and 2015 the population that speaks Spanish at home in America grew from 31m to 37m. But during the same period the share of all Spanish-speaking Hispanics who speak Spanish at home shrank by five percentage points, from 78% to 73%. Data from the Pew Research Centre show that, in 2000, 48% of Latino adults aged 50 to 68 and 73% of Latino children aged 5 to 17 spoke “only English” or “English very well”. By 2014 those figures had increased to 52% and 88%. The explanation has a lot to do with changing demography. Net migration to America from Mexico has been negative since the end of the financial crisis. More Hispanics in America today were born in the United States than arrived from other countries as immigrants, making them less likely to speak Spanish at home—or at all. In 2000, 59.9% of Latinos were born in America. By 2015 that share jumped to 65.6%. Lower birth rates and a stronger economy in Mexico mean such trends are likely to continue, rendering the future of Spanish in the United States uncertain."
Again, from article: "In his well-known study on “linguistic life expectancies” in southern California in 2006, Rubén Rumbaut, a professor at the University of California, Irvine, found that Spanish was following the same trajectory as other languages in America had—just more slowly. He established that only 5% of fourth-generation Mexican-Americans in southern California could speak Spanish very well: “After at least 50 years of continuous Mexican migration into southern California, Spanish appears to draw its last breath in the third generation.”