Denmark's Wozniacki retired in 2020 to raise a family and delighted fans as she announced her return to competitive tennis earlier this year, earning a wildcard to the year's final major.
She cruised through her opener to set up a showdown on Arthur Ashe Stadium with the 11th-seed Kvitova, whom she trails 8-6 in career head-to-head but has not faced since the beating her during the WTA Finals five years ago.
"I actually didn't know that I had the potential of playing her in the second round. I don't think she knew it either," said Wozniacki, a runner-up twice at Flushing Meadows.
"We've been around for a long time. We've played each other many times. I think at the end of the day we're just out there to do our best and compete."
The two fan favourites are no strangers to the spotlight, after Kvitova ended Wozniacki's 2016 Olympic campaign in the second round and beat her in the fourth round of Wimbledon in 2010.
"I know exactly what I need to do. I know where my game needs to be at to beat Petra. There's definitely a calmness to knowing that," said Wozniacki.
Ninth seed Taylor Fritz (25) and 10th seed Frances Tiafoe (25) represent the United States' best hope of ending a 20-year American men's Grand Slam drought and are another highlight to the evening program in New York.
Fritz closes out the action on Louis Armstrong Stadium against unseeded Peruvian Juan Pablo Varillas (27) while Tiafoe kicks off the evening programme on Arthur Ashe Stadium against 58th-ranked Austrian Sebastian Ofner (27).
"There is always going to be a lot of pressure, just as an American playing the US Open," Fritz told reporters.
"There is no other way to put it. Like obviously all the Grand Slams are equal in points, but for an American, the US Open is always going to be the most important one."
It is the first meeting for both pairs, and a welcome return to the night-time spotlight for Tiafoe, a year after his surprise run to semi-final made him the breakout star of the tournament.
Early rain mercifully gave way to clear conditions in time for the outdoor action on Wednesday, as fans showed up in droves for the first day of the second round.
Second seed Novak Djokovic (36) has already reclaimed the world number one ranking with a convincing straight-sets win over Frenchman Alexandre Muller (26) and will hope to continue his march towards matching Margaret Court's record haul of 24 Grand Slams.
He faces Spain's Bernabe Zapata Miralles (26) second on Ashe on the dayside schedule after his young rival, Carlos Alcaraz (20), cruised to the second round as his German opponent Dominik Koepfer (29) retired injured on Tuesday.
The Serb has been beaten only once in 22 hard-court matches so far this season and should have little problem with the 76th-ranked Zapata Miralles.
Djokovic is back at the tournament after U.S. COVID travel restrictions left him unable to compete last year.
