True. There is, and always has been, a very powerful Americanization force in this nation, thank God. It has always transformed the language and culture of immigrants to American. That's as it should be. If they should have kept their language and culture then they should have stayed in the country they came from.
As for the Arabic Muslims, they are an enemy within the gates insofar as they don't assimilate, and the incarceration of the Japanese Americans in WWII comes to mind as a solution. They could be offered the option of going back where they came from. What nation has survived a Trojan horse?
However, the continued massive influx of Mexicans and other Latin Americans has created a certain critical mass that has caused the assimilation process to slow and reverse. With Spanish language media far more available and ubiquitous than was, say, the old Yiddish or Italian press and theater, governments willing to provide information in Spanish, in sharp contrast with the "English only" prevalent in government during the 1880-1920 immigration wave, and the creation of vast Hispanic barrios where one seldom sees a non-Hispanic and then only as a merchant or a government employee, Hispanics can live an entirely separate life detached from the mainstream U.S. culture. Their only effective connection with Americans is through the workplace, and with minimal English and/or Spanish speaking supervisors, they will be able to seek and keep employment. In time, the political figures in the Southwest will become Hispanic, and even the historically Irish dominated Catholic hierarchy will become more Latin. The days of governors named Schwarzenegger and Perry are numbered in the Southwestern U.S. So are the days of Catholic bishops named Mahoney or Grahmann.
As areas, even whole sections of states, become Hispanic dominated, non-Hispanics leave. During the 1990s and early 2000s, there was a net outflow of African Americans from New York due to the increased numbers of Hispanics in the blue collar and service jobs that blacks traditionally had held. There has been quiet, yet evident, "white flight" from increasingly Hispanic South Texas and Southwest Texas, as well as Southern California.
There is a numerical limit to the number of immigrants that can and will leave Latin America. However, immigration must be brought under control so we Americans do not find out where that numerical limit is. Additionally, without such controls, the Hispanic culture will become a parallel one to traditional American culture, and a dominant culture from Dallas and Houston to Los Angeles and Las Vegas. With controls, the assimilation process can restart. Although many condemn the 1920 immigration controls as racist, since it favored northern and western European nations, the 45 year "dry spell" of immigration caused by these controls greatly facilitated the Americanization of the millions of Eastern Europeans, Jews, and Italians who had immigrated over the prior four decades, as these ethnic communities no longer had reinforcements who reconnected them with the "old country". What worked then can work now.