World 400m champion Jeremy Wariner claimed his second gold in Helsinki as he brought home a flawless American display in the men's 4x400m relay.
The US quartet of Andrew Rock, Derrick Brew, Darold Williamson and Wariner came home in two minutes 56.91 seconds - the world's fastest time this year.
The Bahamas were unchallenged for the silver while Jamaica battled it out with Great Britain for third spot.
Davian Clarke finally shook off Malachi Davis to seal bronze for Jamaica.
Tim Benjamin, who came fifth in the 400m individual final, tried to get Britain off to a flying start with a time of 45.00.
But the team's tactics did not pay off as they could not stay in the medal position despite brilliant legs from Martyn Rooney (44.80) and Robert Tobin (44.60).
"I went on the first leg in order to get the guys up there," Benjamin told BBC Sport.
"It wasn't to be and I'm truly gutted because we ran a great time."
Davis, who ran a decent final leg but could not close down Jamaica's Clarke, added: "Everyone did their best which is all that you can ask for."
Wariner felt every member of the US quartet contributed to their victory.
"I feel really great about how we won," he said.
"Each leg set us up to get in position."
But he admitted he came under pressure on the last leg.
"On the 200m mark I looked up and I noticed Chris Brown (of the Bahamas) and Jamaica were right on my back," he said.
"So I had to stay focused and run a flawless last 200m."