Former teammates Aly Raisman and McKayla Maroney also appeared before the committee, along with FBI Director Christopher Wray.
The committee is examining shortcomings in the FBI's investigation into Nassar, later convicted of sexually abusing girls.
He is serving a life sentence in jail.
"I blame Larry Nasser, and I also blame an entire system that enabled and perpetrated [sic] his abuse," said Ms Biles, the most decorated Olympic gymnast of all-time.
"If you allow a predator to harm children, the consequences will be swift and severe," she added.