Russians Top Biles, Americans in Gymnastics Qualifying

Simone Biles, of the United States, reacts after performing on the uneven bars during the women's artistic gymnastic qualifications at the 2020 Summer Olympics, in Tokyo, on July 25, 2021. Gregory Bull/AP Photo

TOKYO—The trouble started early. A step out of bounds on floor exercise here. A short landing there.

Over the course of two hours on Sunday, the mistakes—some almost imperceptible, some laid bare for the world to see—kept piling up, chipping away at the aura USA Gymnastics has built over the past decade. Not even the greatest of all time was immune to the realities of a sport where perfection is unattainable.