The 18-year-old winger, who was born in Tampa, Florida to an American father and German mother, trained with the USA earlier this month before the national team's friendly against Ukraine.
"Obviously this was a big decision, and I spent a long time discussing it with my family," Green said in a news release. "I was born in Florida and my father still lives there, so I have deep roots in the U.S. and I'm very proud to be representing the United States.
"A big part of the decision was the experience I had in Frankfurt. All the players were super nice and welcomed me from the beginning. Clint Dempsey gave me a jersey with my name on it, and the way they supported me gave me a lot of belief. The coaches have shown a lot of trust in me and now I hope to do everything I can to earn a spot on the World Cup roster."
U.S. Soccer made the announcement Tuesday after Klinsmann revealed the news on Twitter.
Green made his first-team debut for Bayern in a Champions League match in November but is yet to feature in the Bundesliga. He plays regularly for Bayern's reserve side. Although he most recently represented Germany at youth level, he did play for the U.S. Under-18 side in a September 2012 friendly.
“We are absolutely thrilled that Julian Green has chosen to be a part of the U.S. National Team Programs!"— Jürgen Klinsmann (@J_Klinsmann) March 18, 2014
The one-time switch is required because Green played for Germany this past fall in U-19 European Championship qualifying, an official competition.
The player will join the USA for their friendly against Mexico on April 2 in Glendale, Arizona, although it remains to be seen if his switch will be approved in time for him to play.
"He is a very special talent," Klinsmann said. "We wanted him to feel comfortable with our program and listen to his heart when making this decision. I personally want to thank Kalle Rummenigge and everyone at Bayern Munich for their support through this process. He is an exciting player with a tremendously bright future."