Anderson, a 20-year-old midfielder who has been at Newcastle since the age of eight, capitalised on miscommunication in Brighton's defence to net a close-range equaliser in the 86th minute.
It was a great moment for the mass of Newcastle fans it happened right in front of at the Red Bull Arena.
"It's been a good tournament for me," Anderson, who finishes the tournament with three goals, said post-match.
"I'm just trying to impress when I can, working hard in the off-season. I've been trying to add goals to my game and it's paying off."
Brighton will feel disappointed to lose the match having dominated possession, having 65 per cent of the ball, and producing more shots, by 19 to 14.
Their goal was scored by Danny Welbeck, who tapped into an empty net after a surging run and cross by Kaoru Mitoma. It was the second time the pair had combined for a goal in the United States tournament.
"I thought he did really well," Eddie Howe said of Barnes. "He was a constant threat in the game. He could have scored a couple of goals, I was pleased."
The result means Newcastle finish the Summer Series unbeaten, having come from behind in all three matches, winning one and drawing two. They top the table heading into the final day of action on Sunday in Landover.