United led 4-0 at the half and held on as Celtic Silver scored three unanswered goals, the last with about a minute remaining.
Coach Mario Ramirez said his United team played equally well in both halves.
"(Celtic Silver) just came out more aggressive in the second half, that's all," he said. "Our kids played fantastic."
The White team's other goals were scored by Madison Grieb _ who also assisted on Alex's second goal _ and Riley List.