U.S. pairs silver medalists Tarah Kayne and Danny O’Shea were also replaced by U.S. bronze medalists Deanna Stellato and Nathan Bartholomay. They join U.S champions and Olympians Alexa Scimeca Knierim and Christopher Knierim on the team.
Chen, 18, placed 11th in PyeongChang, right behind teammates Bradie Tennell and Mirai Nagasu, who Bell joins on the world team.
Chen was third at nationals in January, but her real breakout was last winter, when Chen won the U.S. title and placed fourth at the world championships.
Bell missed the Olympic team after placing fifth at the U.S. Championships in January, one year after taking silver at Skate America and bronze at nationals.
Bell was the second alternate for worlds after Sochi Olympian Ashley Wagner, who did not take the spot vacated by Chen.
The medal contenders at worlds in Milan are led by Russian Olympic champion Alina Zagitova, Olympic bronze medalist Kaetlyn Osmond of Canada, Japanese Satoko Miyahara and Italian Carolina Kostner.
If Serena Williams is to win a record-tying 24th Grand Slam singles title at the French Open, she may have to go through her older sister in the fourth round.
Williams, the sixth seed, could play Venus Williams in the round of 16 at Roland Garros, which begins Sunday.
Serena opens against countrywoman Kristie Ahn, whom she beat in the first round at the U.S. Open. Serena could then get her U.S. Open quarterfinal opponent, fellow mom Tsvetana Pironkova of Bulgaria, in the second round.
If Venus is to reach the fourth round, she must potentially get past U.S. Open runner-up Victoria Azarenka in the second round. Azarenka beat Serena in the U.S. Open semifinals, ending the American’s latest bid to tie Margaret Court‘s major titles record.
Venus lost in the French Open first round the last two years.
The French Open top seed is 2018 champion Simona Halep, who could play 2019 semifinalist Amanda Anisimova in the third round.
Coco Gauff, the rising 16-year-old American, gets 2019 semifinalist Jo Konta of Great Britain in the first round in the same quarter of the draw as Halep.
The field lacks defending champion Ash Barty of Australia, not traveling due to the coronavirus pandemic.
Also out: U.S. Open winner Naomi Osaka, citing a sore hamstring and tight turnaround from prevailing in New York two weeks ago.
Rafael Nadal was put into the same half of the French Open draw as fellow 2018 and 2019 finalist Dominic Thiem of Austria, with top-ranked Novak Djokovic catching a break.
Nadal, trying to tie Roger Federer‘s male record 20 Grand Slam singles titles, could play sixth-seeded German Alexander Zverev in the quarterfinals before a potential clash with Thiem, who just won the U.S. Open.
Djokovic, who is undefeated in 2020 save being defaulted out of the U.S. Open, could play No. 7 seed Matteo Berrettini of Italy in the quarterfinals before a possible semifinal with Russian Daniil Medvedev.
Medvedev is the fourth seed but is 0-3 at the French Open. Another possible Djokovic semifinal opponent is fifth seed Stefanos Tsitsipas of Greece, who reached the fourth round last year.
The most anticipated first-round matchup is between three-time major champion Andy Murray and 2015 French Open champion Stan Wawrinka. In Murray’s most recent French Open match, he lost in five sets to Wawrinka in the 2017 semifinals.