Much of the population of this country is of migrant stock. Some are newly arrived, while others are the progeny of immigrants (such as I am).
The newly arrived naturally favor speaking their native tongues until they gain proficiency and confidence in the English language. Their children and grandchildren who grow up here may turn out to be fully bilingual. On the other hand, they may, to one extent or another, lose the language of their parents and grandparents as they become fully assimilated into the American fabric.