A product of the USNTDP system, Porter made his international debut with the United States as a young 17-year-old in the 2003 World Under 18 Championships in Yaroslavl, Russia. After posting 2 points in 6 games to finish out of the medals, in fourth place, Kevin returned in his final year with the Development Program to play in the succeeding 2004 World Under 18 Championships in Minsk, Belarus. In a prominent senior role, Kevin scored 2 goals and 6 assists to place second on the team with 8 points as USA went on to claim the Silver medal, losing 3–2 to Russia in the final on April 18, 2004.