In August at the 2018 U.S. National Championships, McCusker won the bronze medal in the all-around behind Biles and Morgan Hurd. She also won the silver medal on bars behind Biles, the bronze medal on beam behind Biles and Kara Eaker, and she placed seventh on floor. In October, McCusker participated in the World Team Selection Camp. She placed first on bars, second in the all-around behind Biles, second on beam behind Eaker, third on floor behind Biles and Grace McCallum, and seventh on vault. The following day, she was named to the 2018 World team alongside Biles, Hurd, McCallum, Eaker, and alternate Ragan Smith.