During the qualification round at the 2018 World Championships, McCusker placed eighth in the all-around after falling off beam and having a sub-par bars performance. She did not qualify to the All-Around Final due to teammates Biles and Hurd placing higher than her. During the Team Final, McCusker competed on bars and beam. She rebounded from her troubles in the qualification round to contribute scores of 14.500 on bars and 13.733 on beam towards the U.S. team's total. Her bars score was the second highest of the day behind Biles and tied with two-time Olympic bars champion Aliya Mustafina. The U.S. won the gold medal with a score of 171.629, 8.766 points ahead of second place Russia, beating previous margin of victory records set in the open-ended code of points era at the 2014 World Championships (6.693) and the 2016 Olympic Games (8.209).