The thing is, immigrants of the past wanted to be AMERICANS...they learned the language and culture as soon as possible. They had their old country traditions, recipes, history, ect. which they kept and passed down, but when they came here they became Americans. Now they do not want to become Americans, they want to bring their third world countries (plural because it is not just people from Mexico that do this) with them. What about our culture? We are losing our culture with this salad bowl liberal multiculturalism nonsense.
I see your point. But, English or not, keep in mind that they were singing an American, patriotic song. The fact that they were singing in their native language does not, to me, seem like a rejection of American culture, nor is it unique to the current wave of immigrants - historically the pattern has been that (1) first generation immigrants have largely spoken their native tongue, picking up a bit of English; (2) second-generation immigrants speak English in public and the native tongue at home; and (3) third-generation speaks mostly English, retaining just a bit of the mother tongue.