The US has immigration controls on all international departures.
However these immigration controls are normally only carried our electronically. When you check-in for your flight (which for an international flight must be done at least 60 minutes before departure), the airline passes your details - including passport details - to US Department of Homeland Security (DHS), who then share it will other groups such as US Customs and Border Patrol (CBP).
In most cases, DHS will notify the airline that they are OK to issue a boarding pass, however if for some reason they determine the passenger is not able to depart the country they can electronically block the issuing of a boarding pass, and force the airline or the passenger to contact DHS/CBP first.
Alternatively, CBP/DHS/TSA staff have the ability to carry out physical checks whilst passengers are boarding a flight, which is normally done on the jet-bridge to the plane (at a point where the passengers are normally not aware that these checks are occurring until they are already on the jet bridge and committed to boarding the flight).
In all cases, once the flight departs from the US, the airlines once again notify DHS which passengers departed on the flight (not including any that did not board, etc), at which point the various government departments are able to update records related to when the person departed the US.
So no you will not need to pass through physical immigration controls as you're probably used to in most countries around the world. Your passport will still be scanned, only by the airline at check-in rather than immigration officials. You ID will still be checked, once by TSA when passing through security, and a second time whilst boarding your flight.