Erik Johnson of the Colorado Avalanche and Matt Niskanen of the Washington Capitals were the other defensemen named.
Those seven players round out the 23-man roster for Team USA. The first 16 players were named March 2.
Backes, a member of the 2010 and 2014 U.S. Olympic teams, was eliminated from the Stanley Cup Playoffs on Wednesday, two wins short of reaching the Stanley Cup Final for the first time. The center had seven goals and 14 points in 20 playoff games.
Jack Johnson played in the 2010 Olympics. He had six goals and eight assists in 60 NHL games this season. Erik Johnson also played in the 2010 Olympics. He had 11 goals and 16 assists in 73 NHL games this season.
Callahan, a right wing, also was a member of the 2010 Olympic team. But hip surgery in June will force him to miss the tournament. Kyle Palmieri of the New Jersey Devils was named as Callahan's replacement on July 20.
Van Riemsdyk, a left wing, played on the 2014 Olympic team and had seven points in six games. Dubinsky, a center, played for the United States at the World Championship in 2008 and 2010.
The 2016 World Cup of Hockey will be played Sept. 17 to Oct. 1 at Air Canada Centre in Toronto. All games will be televised by ESPN in the United States and Sportsnet and TVA Sports in Canada.
Here is the entire Team USA roster (alphabetically by position):
Forwards:
Justin Abdelkader, Detroit Red Wings; David Backes, St. Louis Blues; Kyle Palmieri, New Jersey Devils; Brandon Dubinsky, Columbus Blue Jackets; Patrick Kane, Chicago Blackhawks; Ryan Kesler, Anaheim Ducks; T.J. Oshie, Washington Capitals; Max Pacioretty, Montreal Canadiens; Zach Parise, Minnesota Wild; Joe Pavelski, San Jose Sharks; Derek Stepan, New York Rangers; James van Riemsdyk, Toronto Maple Leafs; Blake Wheeler, Winnipeg Jets
Defensemen:
Dustin Byfuglien, Winnipeg Jets; John Carlson, Washington Capitals; Erik Johnson, Colorado Avalanche; Jack Johnson, Columbus Blue Jackets; Ryan McDonagh, New York Rangers; Matt Niskanen, Washington Capitals; Ryan Suter, Minnesota Wild
Goalies:
Ben Bishop, Tampa Bay Lightning; Jonathan Quick, Los Angeles Kings; Cory Schneider, New Jersey Devils
