As a product of the US NTDP, Johnson first made his international debut for the United States at the 2005 World U17 Hockey Challenge. In the same year, he captured a gold medal as a 17-year-old at the 2005 World Under-18 Championships. Johnson scored ten points in six games the 2006 World Under-18 championships to help the U.S. retain the gold medal, and was selected as the Bob Johnson Award winner as the Best American player in international competition.