Stack played in all five games contested by the Team USA in the 2010 Winter Olympics. She accumulated eight points, five assists and three goals, with four points in the game against Russia. Team USA went on to win a silver medal, losing to Canada in the gold medal game 0–2. In the second game of the 2011 IIHF Eight Nations Tournament, Stack was one of two US players to register a hat trick in a victory over Japan. In the first game of the 2012 IIHF Women's World Championship, she had three assists in a 9–2 victory over Canada. In a game versus Finland at the 2012 Worlds, she scored a hat trick and added three assists in an 11–0 victory.