Why is it wrong to think you should know english if you live in America?

I really hate it when people come here, and don't even try to learn English! I don't think it's wrong to think people should learn English! My maternal grandfather came here from Colombia when he was like maybe 60 years old, and although he kinda came off as not really speaking a lot of English he probably understood a lot more than he could speak. When my grandfather died I saw all of his note books where he had been practicing, and writing English, and it was very inspiring to me. I get very frustrated with much younger people who are in their prime who don't even freaking try to learn English! I think everyone should try to learn a second, or even a third language, but here in the United States there's no excuse for people not learning, or at least trying to learn English!