More than 1,000 Rangers fans watched their side fall behind in first-half injury-time as Carlos Martinez curled home from 20 yards for the team from the third tier of United States soccer.
With the game being played in the shadow of the California State Fair, Darren McGregor headed an equaliser from Lewis Macleod's corner early in the second half before Black flicked home Kenny Miller's cutback to win it for Rangers.
Manager Ally McCoist paid tribute to the fans who travelled to watch the game.
“I’m happy with the result for a lot of the supporters who have travelled. We had a fantastic support at the game," he told the club's website.
“We had guys and girls coming up from Los Angeles, San Diego, San Francisco and Texas. They came from all over the place including down from Vancouver too.
“You can say what you like and I know it’s a pre-season game but you want to give them a level of performance and a result. We certainly did that in the second half.
“We were slow to get going again in the first half and I don’t know if the surroundings didn’t help or whatever. We were miles better in the second half though.”