In the upper class vehicles like the Mercedes S-Class this system is more than 10 years already available. Already in small cars like the Volkswagen Golf (i don't know if such a small car is sold in the US) the system is available.

My friend has a VW Golf GTD (2000ccm and 200HP Diesel with 7 gears) and this car also has such automatical systems. The lane system only works if the lanes are "painted" on the street. If so there is a symbol in the cockpit of the car showing that the system has recognized them. He can take the hands of the wheel and if a curve is coming the car automatically keeps his track. After about 50 seconds there is a signal making an alert that he shall take his hands back on the steering wheel.

There is also a radar system for the cruise control. It automatically accelerates and reduces speed if there is another car/object in front of you. This also includes the braking help if suddenly an object appears on your way.