The LA Galaxy forward criticised the way the USA team were set up to play at the World Cup in Brazil and said he would have challenged the coach if he had been picked for the team
The Americans were eliminated from the tournament in Brazil after being beaten 2-1 by Belgium in extra time on Tuesday.
Despite being knocked out in the second round, Klinsmann's team gained plenty of praise for their passionate performances in Brazil.
However, Donovan – who is the USA's all-time leading goalscorer – felt that Klinsmann did not adopt the right approach during the competition.
The 32-year-old LA Galaxy forward, who was overlooked by the German coach for USA’s World Cup squad, said: "It's certainly a missed opportunity.
"The thought of having a game on Saturday – the day after July 4th – against [Lionel] Messi and Argentina, with what was already a swelling audience, would have been incredible.
"I think we're all disappointed in what happened yesterday. I think the most disappointing is we didn't seem like we gave it a real effort, from a tactical standpoint.
"I thought the guys did everything they could, they did everything that was asked of them, but I don't think we were set up to succeed yesterday, and that was tough to watch."
Donovan added: "It's a results-oriented business, and so, results-wise, you can hold your head high.
"But, if you really look at the performances, there were some good performances by guys, some not-so-good performances by guys. As a whole, I think tactically, the team was not set up to succeed.
"They were set up in a way that was opposite from what they've been the past couple years, which is opening up, passing, attacking – trying to do that. And the team's been successful that way.
"Why they decided to switch that in the World Cup, none of us will know. From a playing standpoint, I think the guys will probably be disappointed in the way things went."
Donovan – who scored 57 goals in 156 international appearances across three World Cups – admitted he would have questioned Klinsmann over the team's formation if he had been picked for the squad in Brazil.
"If I'm in that locker room before that game – before the Germany game, before the Belgium game – and the coach walked in and said we're playing a 4-5-1 and Clint [Dempsey] is up top by himself, I would have been disappointed.
"Because I would have said 'Let's go for it. I want a chance to go for it and try to win the game'."