Bruce Arena identified Jan Koller's early goal as the crucial moment in the USA's 3-0 loss to the Czech Republic and was critical of Landon Donovan.
Koller struck five minutes into their World Cup opener and coach Arena said: "It was a bad start to the tournament.
"When you concede after five minutes against a team which defends well and puts on the pressure, it's difficult.
"Landon showed no aggression. I am very disappointed by the performance of our players. The best team won."
Skipper Claudio Reyna added: "Their first goal put us back on our heels.
"We played well and hit the post but we then made some tactical changes which didn't work. We needed some width and couldn't get it."
Reyna, who struck the post after 27 minuntes when the USA were still just 1-0 down, says the team need to put the experience they gained from the defeat to come out fighting in their next match against Italy.
"They will be tough to beat but we have to bounce back and learn from this," he added.
"Some of the guys in the team are new to the World Cup and they were a little nervous.
It would be a bit of a miracle now if they got through this group
Former USA international
"Now we must look forward and see what we are made of. We will have to be aggressive and not hesitant."
The USA meet Italy on Saturday in Kaiserslautern, before a final group game against Ghana.
Former international goalkeeper Brad Friedel believes his compatriots now need a "miracle" if they are to qualify.
"There's been a lot of hype based on the last performance in the 2002 World Cup, but we've now a lot of guys who we didn't know what was going to come from them," the Blackburn stopper told Five Live Sport.
"The Czech Republic did their homework on DaMarcus Beasley and Landon Donovan and they didn't really touch the ball. Overall we were second best in every department.
"I thought from the get go that to get out of the group they would have needed a draw in the first game to set themselves up with some confidence and get off to a good start.
"They didn't do that and it would be a bit of a miracle now if they got through this group."