The United States led from start to finish to clinch Olympic gold in the women's eight at Eton Dorney.
The team, who have not been beaten in four years, posted a time of six minutes 10.59 seconds to retain the Olympic title they won in Beijing.
Canada's boat finished in the silver spot in a time of 6:12.06, while Netherlands took bronze in 6:13.12.
Britain's eight, who won bronze at the 2011 world championships, were never in touch with the leaders, coming fifth.
"Yeah! That is an American dynasty, baby. It was a great race, a little tough conditions, but it was awesome - a lot of power in that boat," said USA gold-medal winning rower Zsuzsanna Francia.
The Canada boat tried to close the gap on their neighbours, but could not find the required burst in the final 500m.
"It's pretty amazing, we did what we could on the day, and it's a silver medal at the Olympic Games," said Canada rower Darcy Marquardt.
"You know what, we were as best prepared as we could have been, each of us having PB [personal best] after PB."
Britain's Katherine Copeland and Sophie Hosking recovered from a slow start to row through Greece in the final 500m and win their double scull semi-final.
The British pair, who only started rowing together two months ago, looked strong in their first heat and continued that strong form to qualify for Saturday's final.
Their winning time of seven minutes 05.90 was the fastest of the women's semi-finals to confirm their status as one of the favourites for gold.