President Biden nominated Sung to the seat to be vacated by Judge Susan P. Graber, who announced her intent to assume senior status upon confirmation of a successor.

[6] During the hearing, senators questioned her about her decision to sign a letter regarding Brett Kavanaugh's nomination to the U.S. Supreme Court.

The letter accused Kavanaugh of being an "intellectually and morally bankrupt ideologue" and claimed that "people will die if he is confirmed".

[11][12] On November 3, 2021, the United States Senate discharged the committee from further consideration of her nomination by a 49–49 vote, with Vice President Kamala Harris breaking the tie.

[18] On September 26, 2022, Sung dissented on an en banc panel in a 8–3 decision that held that California AB 32, a law that banned private, for-profit prison and immigration detention centers within the state, was unconstitutional.