In another ignorant email I received today on immigrants the originator claimed that those that came in the mass immigrations from Eastern and Southern Europe in the late 1800's and early to mid 20th century soon learned to speak English.
In fact, many who settled in large citues such as New York, Chicago, Pittsburgh settled in enclaves (barrios, if you wish) and only spoke English when absolutely necessary. Every day dealings were with others who spoke the native tongue. Even in smaller communities, there were mothers who rarely set foot out of the home and so never learned to speak English.
I remember my great uncle's neighboring farmers were German immigrants. The mother rarely left the farm and never learned to speak English. When I was in high school in a small city in Ohio, I had good friends who came from Greece, Italy and Serbia, none of the mothers spoke any English. When I visited their homes, my friends translated between me and their mothers. Even if the fathers were at home, only the native tongue was spoken.
Most of us want to converse, communicate in the language which is native to us. In that we are most comfortable. When Americans live in large numbers in a foreign country they tend to live closely together and to speak only English to each other. Why would immigrants to this country be any diffrent?