Since you're from the UK, I'll assume things may not work exactly the same over there. The reality is, this kind of law needs to be passed in the US because we live in such a litigious society. There are jobs where everyone needs to speak the same language, and be clear on communication, or someone gets hurt or killed. However, I can guarantee you there will be some slip-and-fall lawyer who will file a lawsuit against a company who forces its workers to communicate in English only, because it's discriminatory. This law is merely protection for employers who need to enforce clear communications among employees. It's not a law to force people to forget their native language if it's not English or lose their heritage, it's just a common-sense law that has to be passed because in America, common-sense does not rule the day.