What makes you think that you can't drink US tap water? I've been drinking it my whole life. The area that I live in has very good tap water. The water department even sends me detailed reports periodically.
For conveniently drinking out of them and filling water bottles in public buildings like schools and hospitals. They're really common in NA, what part of the world are you in?
By googling it, it seems these will filter out some forever chemicals that are a problem pretty much everywhere. It will also cool the water, which might be beneficial if your tap water is a bit on the warmer side (which mine is and it's infuriating, I want to drink near-freezing water)
Note: I'm not American and don't have one of these, just googling.