Actually, we do have what they call "Screeners" in the United States (at least in New Jersey). They work out of a local Psychiatric ER and will come out (with a police officer) to assess the person for danger to self or others. If danger is detected, they can call an ambulance which will transport the person to the ER with paperwork from the Screener recommending hospitalization. If the person is resistant, the police can use force to subdue the person and take them in the police car. In the ER, the doctor must assess the client within 24 hours and if they agree with the screeners, the person can be involuntarily committed.