Certainly the most important reason that any player should be selected for a World Cup roster is that they can help their team win games. And while Green certainly has a lot to prove, the U.S. is going to need a spark plug off the bench.
On the wings, the U.S. will likely have Landon Donovan, Graham Zusi and Alejandro Bedoya to choose from. Donovan is still a great player, but he no longer has the speed that once helped him terrorize defenses. And Zusi, while he plays with great effort and provides excellent service from the flank, also tends to play the game at one speed.
Bedoya has gotten regular playing time in France this season, but he has had a series of underwhelming performances for the national team over the past several months.
The U.S. and head coach Jurgen Klinsmann are going to need someone off the bench who can provide a spark by running at defenders and creating chances.
It's hard to say with certainty that Green is the man for the job due to his lack of experience, but considering the U.S.'s other options, he's probably the best they've got.