In 2019, she competed at the Birmingham FIG World Cup, earning a silver medal in the all-around behind Olympic champion Aliya Mustafina.

In February McCusker was named as the wildcard athlete for the 2017 AT&T American Cup, an FIG event held on March 4 at the Prudential Center in Newark, New Jersey.

[6] In April, McCusker competed at the City of Jesolo Trophy in Italy, where she won the all-around gold medal with a score of 56.600, finishing ahead of Rebeca Andrade of Brazil.

Due to her injury, she did not compete at her highest level and placed eighth on bars, thirteenth on beam, and fourth on floor.

[10] In August at the 2017 U.S. National Championships, McCusker won the bronze medal in the all-around behind Ragan Smith and Jordan Chiles.

She also won the gold medal on bars, one tenth of a point ahead of Alyona Shchennikova, and she placed fourth on floor behind Biles, Jade Carey, and Morgan Hurd.

[18] The following day, she was named to the 2018 World team alongside Biles, Hurd, McCallum, Eaker, and alternate Ragan Smith.

[19][20] 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.

[24] There, she won the silver medal in the all-around behind Russian gymnast Aliya Mustafina after counting falls on vault and beam.

After the competition, she was officially named to the 2019 Pan American Games team alongside Eaker, Finnegan, Hurd, and Wong.

[28][29] During the all-around final, McCusker won the silver medal behind Ellie Black of Canada after she fell off bars while performing her Ricna.

[30][31] On the first day of event finals, McCusker rebounded from her fall in the all-around to win the gold medal on bars ahead of Wong and Black.

[32][33] On the second day of event finals, McCusker won the bronze medal on beam behind Eaker and Black after she fell on her dismount,[34] and she placed fifth on floor after going out of bounds twice.

[36] On the second day of competition, she competed on vault and uneven bars before her coach decided to pull her from the remaining two events due to McCusker feeling sick to her stomach.

[40] As a result, McCusker announced on Instagram that she would finish her elite career training at Arizona Sunrays alongside fellow national team member Jade Carey.

[42] In May McCusker announced that she will defer attending the University of Florida until after the Olympic Games, which were postponed until 2021 due to the COVID-19 pandemic, starting in the 2021–22 school year.

[43] In November news broke that McCusker had sued her former coaches, Maggie Haney and Victoria Levine, for negligence, intentional infliction of emotional distress, and assault.

McCusker cited how Haney forced her to train with an injured wrist in April 2017, an injured hamstring and a fractured ischium in the months leading up to the 2017 World Championships, foot fractures in early 2018, a torn supraspinous ligament in early 2019, and forced McCusker to train and compete at the 2019 U.S. Classic and 2019 Pan American Games while being diagnosed with exercise-induced rhabdomyolysis.

[49] McCusker made her NCAA debut on January 7 in a quad meet against Rutgers, Northern Illinois, and Texas Women's.

On March 14 she was named SEC specialist of the week after posting a 9.95 on the balance beam and a 9.925 on the uneven bars during a quad meeting held at Texas Woman's University.