Donovan, 32, was one of seven players cut from the final roster ahead of the June 2 deadline, despite being the nation's all-time leading goal scorer with 57 goals - 21 ahead of team-mate Clint Dempsey.
The LA Galaxy striker's axing almost certainly spells the end of his international career, having earned 156 caps, which included three World Cup appearances.
Terrence Boyd, Joe Corona, Maurice Edu, Brad Evans, Clarence Goodson and Michael Parkhurst also missed the cut ahead of next week's clash with Azerbaijan (May 27).
Though, Bayern Munich's 18-year-old midfielder Julian Green was a surprise inclusion, having only debuted in a friendly against Mexico in April, and could come up against Germany, Portugal and Ghana in Group G.
"It's an exciting moment when you have narrowed the roster down as a coaching staff, and these 23 players that you've chosen can focus now purely on Brazil," Klinsmann said.
"We can go into more specific things about technical approaches, and about the opponents.
"For the players, it's very important to know that they are now part of it and they can relax and know they are on the list going to Brazil and taking it from there.
"After almost 10 days of work right now, we thought the point has come to make the decision."
Squad in full:
Goalkeepers: Brad Guzan (Aston Villa), Tim Howard (Everton), Nick Rimando (Real Salt Lake)
Defenders: DaMarcus Beasley (Puebla), Matt Besler (Sporting Kansas City), John Brooks (Hertha Berlin), Geoff Cameron (Stoke City), Timmy Chandler (Nürnberg), Omar Gonzalez (LA Galaxy), Fabian Johnson (Borussia Monchengladbach), DeAndre Yedlin (Seattle Sounders FC)
Midfielders: Kyle Beckerman (Real Salt Lake), Alejandro Bedoya (Nantes), Michael Bradley (Toronto FC), Brad Davis (Houston Dynamo), Mix Diskerud (Rosenborg), Julian Green (Bayern Munich), Jermaine Jones (Besiktas), Graham Zusi (Sporting Kansas City)
Forwards: Jozy Altidore (Sunderland), Clint Dempsey (Seattle Sounders FC), Aron Johannsson (AZ Alkmaar), Chris Wondolowski (San Jose Earthquakes)
