There was a Washington Post article talking about the unusual position Klinsmann is in...
Do Americans want to blow their load on sending out an old man at the cost of taking away experience from an 18 year old who is likely going to be the face of American soccer for the next 15 years? It sucks. But it's business.
The dilemma is deeper than this. Does Klinsmann think that Donavon on the bench is enough to get the team out of group play? If not, then might as well play for 2018. But taking away (limited) experience from an 18 year-old shouldn't keep the 18 year-old from being the face of American soccer for the next 15 years if he's playing in Europe and that darn talented.