Just one piece of paper, a license which I assume you already carry. Any law enforcement officer can ask to see it at any time today, so what is the difference if those that may look like they are here illegaly, get bothered to prove they are legal? It would prod them to assimilate into our culture, and make them EXTREMELY uncomfortable if they cannot communicate in the language of the land.
Actually, no... I'm not just randomly asked for my papers by law enforcement, and I don't think I'd like it if I was.