A LABOR MP was king-hit, thrown against a car and bashed in the carpark of a suburban McDonald's.

The New South Wales MP claimed his American assailant repeatedly told him "this is how we do it in America" during Sunday's attack outside the fast-food restaurant in Thornleigh, in Sydney's north.

Paul Gibson, who reported the incident to police, said he was lucky to survive the attack, which knocked him out.

"How he didn't kill me I don't know," he said, adding that he and a female companion were parking after a function when he gave the man sitting in the next car a "friendly toot".

The man then got out and guided Mr Gibson in.

The MP for Blacktown said the man then accused him of running over his foot, before king-hitting him.

He said the man grabbed him by the throat, threw him into the bonnet of a 4WD and smashed his head on the cement.

Mr Gibson said the man repeatedly said "this is how we do it in America" as he pounded Mr Gibson's head.

When people came to drag off the attacker, Mr Gibson said "this is how we do it in Australia" and hit the man back, causing him to bleed.

The pair were separated and Mr Gibson claimed he was told by a bystander that the man had a revolver. Mr Gibson and his companion, who he said was a "friend" and would not name, then made a report to police.

Mr Gibson said yesterday: "I got out and he said, 'You ran over my foot'. I said, 'Mate, if I ran over your foot, I'm sorry, are you OK?'

"I went to walk into McDonald's - the next thing I know I'm in la la land. I didn't know if I'd had a heart attack or what.

"Next thing I knew I'm flying through the air. Everyone tells me this bloke's come up, punched me in the back of the head, grabbed me by the throat.

"I could hear him say 'this is how we do it in America, this is how we do it in America.' How he didn't kill me I don't know."

Mr Gibson said he was close to losing consciousness during the attack and has since had X-rays to identify whether he had a broken shoulder and ribs.

Police are appealing for information to identify the attacker.

The man police want to speak to was "of African American appearance, 185-187cm tall, an acne-scarred complexion and with a solid build".