Gillom played for the USA World University Games team in Kobe, Japan in 1985. The team brought home a silver medal, after falling to the USSR. The team trailed by 18 points at one time, mounted a come-back attempt but fell short, losing 87–81. Gillom was the second leading scorer for the USA team, with 12.8 points per game. The following year, Gillom played for the USA team at the World Championships, in Moscow. This time, the USA team would meet the USSR in the title game and emerge victorious, winning the gold medal with a score of 108–88. Gillom averaged 2.8 points per game.
Gillom was named to the team representing the USA at the 1987 Pan American Games, held in Indianapolis, Indiana in August. The USA team won all four of their games winning the gold medal for the event. She averaged 9.5 points per game. Gillom continued with the national team at the 1988 Olympics in Seoul, South Korea, held in September. The team won all five games which resulted in the gold medal. Gillom averaged 2.8 points per game.
Gillom was named assistant coach of the USA National team in preparation for competition in the 2010 World Championships and 2012 Olympics. Because many team members were still playing in the WNBA until just prior to the event, the team had only one day of practice with the entire team before leaving for Ostrava and Karlovy Vary, Czech Republic. Even with limited practice, the team managed to win their first game against Greece by 26 points. The team continued to dominate with victory margins exceeding 20 points in the first five games. Several players shared scoring honors, with Swin Cash, Angel McCoughtry, Maya Moore, Diana Taurasi, Lindsay Whalen, and Sylvia Fowles all ending as high scorer in the first few games. The sixth game was against undefeated Australia—the USA jumped out to a 24 point lead, but the Australian team cut the lead back to single digits late in the game. The USA prevailed 83–75. The USA won their next two games by over thirty points, then faced the host team, the Czech Republic, in the championship game. The USA team had only a five point lead at halftime, which was cut to three points, but the Czechs never got closer, and went on to win the championship and gold medal.