There were also celebrations for Great Britain, who won two silver medals in the regatta and secured two ISAF Sailing World Cup series titles in the Paralympic 2.4mR and Sonar event.
Rick Doerr's USA crew finished seventh and fifth in the last two races of the Sonar class - but that was enough for them to win the regatta from John Robertson's Skandia Team GBR crew, who took silver.
However, a second place finish for Robertson, Hannah Stodel and Steve Thomas was enough to ensure they pipped the Doerr, Hugh Freund and Maureen Mckinnon-Tucker US crew to win the overall ISAF World Cup series.
The French crew skippered by Bruno Jourdren took bronze in the regatta, with the Irish crew skippered by John Twomey, coming third in the World Cup series.
The USA crew suffered early set backs in both of today's races that saw them having to work their way up from the back of the fleet.
"We knew we couldn't be any further back than fifth in the second race. Once we were there we didn't want to do anything too risky.
"We were sharp early in the week and it was a good thing that we put some good results in the bank.
"It's way too early to say we've got any kind of advantage for 2012 after this regatta. If you think you've got an advantage you can become a bit complacent and we're not going to make that mistake."
There were also celebrations for Scott Whitman and Julia Dorsett as the USA crew won gold in the SKUD18 class and took the World Cup series gold. They rounded off an impressive campaign by winning the last two races today. It meant they won five of the seven races and finished second in the two others.
The British crew of Alex Rickham and Niki Birrell finished second in both of today's races to take the silver medal both in the regatta and the World Cup series. John McRoberts and Brenda Hopkin of Canada took bronze in both.
Dorsett said she was delighted to win at Weymouth and Portland. "We're very happy, it feels good," she said. "We knew it was going to be tough.
"The conditions here are very similar to those at home at Newport, Rhode Island, so we felt pretty comfortable.
"We are hopefully going to keep riding the wave for the next three years," she said. "We've learned a lot this week and we feel really confident."
Britain's Rickham said: "We're happy, but at the same time we're slightly disappointed because we had the chance to win gold not silver. It just didn't go our way.
"All in all I think we're in a really good position though. We just need to make sure we are as close to the top as we are now and make sure we're still there in two and a half years.
"Nothing would be nicer to qualify for 2012 and win a medal here at home alongside Nikki, considering our disappointment in Beijing."
Thierry Schmitter of The Netherlands, bronze medallist at the Athens 2004 Paralympic Games, secured gold in the 2.4mR class at the Skandia Sail for Gold Regatta. He finished first and second in the last two races of the series today.
France's Damien Seguin, gold medallist at the Athens Paralympic Games and silver medallist in Beijing, took silver at Weymouth and Portland today.
Another Dutch sailor, André Rademaker, did enough to pip Britain's Megan Pascoe to the bronze. He finished second and third in today's races, with Pascoe finishing fourth in both of the final two races.
But there was significant compensation for Pascoe when she learned her fourth place was just enough to win the overall World Cup series by two points from Schmitter.
"I did my best," said Pascoe. "I could have got into third today, so I was a little bit disappointed. I would have liked to have medalled here, but it's a nice silver lining to win the World Cup series."
A report on the remaining classes, which go through to their Medal Races tomorrow, follows later.
Click here for details on how to follow the Medal Races at the Skandia Sail for Gold Regatta. With live TV coverage for UK viewers, streaming radio and online tracking, there's a multitude of options for following the final, all-important races of the inaugural ISAF Sailing World Cup series.
ISAF Sailing World Cup
The ISAF Sailing World Cup 2008-2009 consists of the following events:
16-21 Dec 2008 - Sail Melbourne The Asia Pacific Regatta, Melbourne, Australia
25-31 Jan 2009 - US SAILING's Rolex Miami OCR, Miami, USA
4-10 April 2009 - Trofeo SAR Princess Sofia MAPFRE, Palma, Spain
18-24 April 2009 - Semaine Olympique Francaise, Hyeres, France
27-31 May 2009 - Delta Lloyd Regatta, Medemblik, Netherlands
20-28 June 2009 - Kieler Woche, Kiel, Germany
14-19 Sept 2009 - Skandia Sail for Gold Regatta, Weymouth, Great Britain
Find out more about the ISAF Sailing World Cup, including the World Cup Standings, more on the seven events, the scoring system and the Notice of Series at www.sailing.org/isafsailingworldcup.