Donovan: Everton loan spell incredible
"Now I know I can play well against anybody," the Los Angeles Galaxy forward told Reuters. "That's a big boost.
"It was an incredible experience. It helps my confidence, absolutely."
A major goal-scoring threat for the Americans for several years, Donovan played a different role at Everton.
"I was relied on to give the team energy, to work hard, defend well and be tactically smart," said the 28-year-old after scoring two goals in 13 games for the English Premier League club to ignite an upturn in their fortunes.
"I think I did all those things," added Donovan in an interview organised by EA Sports.
His arrival coincided with just two league defeats and shock wins over champions Manchester United and Chelsea, and he left with Everton ninth in the table.
Donovan, who had a less successful loan stint in Germany with Bayern Munich last year, said he could not wait for the U.S. to play England in their opening World Cup Group C match in Rustenburg, South Africa on June 12.
"In the history of U.S. soccer it (a shock U.S. World Cup win over England) happened once back in 1950," he said.
"There's not many who can say they have played against England in a World Cup. I want to be one of the ones that says we beat them."
Donovan, who has won a record 120 caps for his country, said the Americans had a good knowledge of England's players and that could work in his team's favour.
"There are quite a few of our guys who have played or are playing in the Premier League right now (so) we have a pretty good gauge of what their players are like and what their styles are," said the forward.
"That's a big thing in a World Cup, how teams' styles are and how you adapt tactically. I think we have a little bit of an advantage that way.
"We know the game is going to be ultra competitive. Both teams play very fast, there's not a lot of standing around on the ball," said Donovan.
His Galaxy team-mate David Beckham will miss England's World Cup campaign with an Achilles problem and Donovan said that was a sign the leading players were being over-worked.
"Top players with top clubs play too many games these days," he said. "That puts a lot of wear and tear on your body.
"Everybody is built differently. Some can play 60 games a year and travel all over the world and it's no big deal, and others can't."
Donovan said Galaxy coach Bruce Arena had been good about giving him time off.
"There are moments when I feel pretty tired and I communicate that," said the forward. "My coaches have been very responsive to that.
"I think when you're honest, coaches appreciate that."