Keller was a member of Team USA that won a gold medal at the 2015 IIHF World U18 Championships. At the 2016 IIHF World U18 Championships, Team USA won the bronze medal and Keller was Team USA's scoring leader. Keller was awarded MVP of the tournament. At the 2017 World Junior Ice Hockey Championships, Team USA won the gold medal and Keller led Team USA in scoring and was named to the tournament All-star team.