If one is here as a citizen legally then why are they here if they don't want to adapt to what the language of our nation is?
It's not rocket science.
I am from Puerto Rico. I speak English, but watch Spanish television to keep my Spanish current. When I was ten and learning English, I watched English television to learn pronunciation and vocabulary. It takes a while to become competent in a new language though. It was nice to be able to get the news and other television in Spanish too.
My experience is that it takes a generation for the new language to take hold. My parents never learned to speak English. I worked hard to learn English because I saw the difficulty my parents had. I keep my Spanish current because it is part of my history and my heritage. I taught my kids to speak Spanish and English. They won’t speak in Spanish and only want to speak English.
Like I said before, Puerto Ricans speak Spanish. Most learn English in school, but all business is conducted in Spanish, and most conversation is in Spanish as well. It doesn’t seem to be causing any trouble to the rest of the US.