Dear reader, I was once an immigrant (not to the USA, because I was born here), but to France. Thus, I spent 16 years of my adult life in a second country. As a polyglot linguist who speaks: US English, fluent French, good Spanish, some German, a little Japanese, and who can read Italian & Portuguese -- I am a proponent of the mandatory official use of US English in the United States of America. Similarly, I encourage everyone to learn several languages.
Having travelled all over the world (and resided in various countries), I underwrite the use of US English as the ONLY legally supported language of the land. I for one, ask newcomers to tolerate and respect the diversity of all origins, but I shall also ask each person to honor the common ground. Wave your national flag (that of your country of origin), but take pause to remember to display "Old Glory". Learn to speak, read, and write US English. Integrate yourself and your cultural identity into the best of the values of your host country (the USA is an amalgum of so many). English is firmly established as a dominant historical and integral part of the national identity (albeit that my ancestors were German [Saxony & Bavaria] and Norwegian).
When one is a visitor (anywhere), or an immigrant to a "new land" -- it is simply polite, good taste to exercise such common sense, i.e. "When in Rome, do as the Romans do".
Cum dilegentia sunt!