Although she has risen to 87th in the world this week, the Belarussian needed the wildcard as she was not ranked high enough when the cutoff for the entry list was made.
It was the same reason Kuznetsova, who won the first of her two Grand Slam titles at the 2004 U.S. Open aged 19, did not gain automatic entry.
The Russian has risen to 88th in the world after collecting her 18th WTA title nine days ago in Washington.
Swiss Wawrinka, a three-time Grand Slam champion, did not defend his 2016 Flushing Meadows title last year because of a knee injury that required surgery last August and kept him sidelined until January.
Since exiting in the second round at Wimbledon, Wawrinka has won only three matches during the American hardcourt campaign.
He fell in the first round in Washington before suffering a third-round loss to world number one and eventual champion Rafael Nadal in Toronto. He is back in action in Cincinnati this week and will face Japan's Kei Nishikori in the second round.
The U.S. Open runs from Aug. 27-Sept. 9.
(Reporting by Frank Pingue in Toronto, editing by Pritha Sarkar)
