Oracle Team USA, owned by software billionaire Larry Ellison of Oracle Corp., essentially starts the match at minus-2, meaning it must win 11 races to retain the oldest trophy in international sports. Team New Zealand must still win nine races to claim the trophy.
Two shore crew members also were expelled, grinder Matt Mitchell was barred from the first four races and the syndicate was fined $250,000.
Kyle Langford, who will replace de Ridder, was given a warning, and another sailor, identified only as Sailor X, had his case dismissed.
Spithill sailed with de Ridder for six years.
"He's one of the hardest-working guys I've ever known, never once had a question about any of his ethics, honest, and one hell of a good guy to race with," Spithill said. "Very, very competitive, and he'll be missed. But Karl's a great guy. We've got a few days to get organized and do what we can."
At 24, Langford is the youngest sailor in the Cup. He has been sailing on the backup boat skippered by Ben Ainslie, the most successful sailor in Olympic history.
Top members of the syndicate, including CEO Russell Coutts, Spithill and tactician John Kostecki, were not implicated in the scandal.
Coutts, a New Zealander who has won the America's Cup four times, told The Associated Press it was an "outrageous decision" by the jury.
"It sets an unbelievable precedent ongoing," Coutts said. "You could think of lots of analogies. Think of Olympic athletes on a team breaking the rules and a whole team getting penalized. It's completely outrageous."
Coutts said de Ridder "has been a fantastic team member and a fantastic sailor for many, many years. All the decisions are incredibly harsh. I don't think the evidence supported the jury's decision."
The jury had harsh words for de Ridder, saying it was "comfortably satisfied" that the Dutch sailor "gave the instruction to add the weight, knew the weight had been added, knew it was a breach of the AC45 class rule and "did not tell the truth in the hearing in this regard."
Although the infractions were from the America's Cup World Series, those races were considered to be held under the overall umbrella of the America's Cup itself.
Team New Zealand managing director Grant Dalton and skipper Dean Barker had both accused Oracle Team USA of cheating.
On Tuesday, they had subdued reactions to the jury verdict.
Dalton said the scandal has "slowly but surely drifted into a non-issue for us because in the end we still have to win nine races. We think that the jury's done a good job. They've been very thorough.
"It's not our problem, never was a problem, and we just get on with it."
