The Prince of Wales and Duchess of Cornwall heard Britons praised at a revamped version of the musical Beach Blanket Babylon, in San Francisco.
Former US Secretary of State George Schultz - playing Superman - said: "Hats off to the British!" and branded Britons "intelligent, not just smart".
The show was redone for Prince Charles and Camilla's first joint tour abroad.
It included lines such as: "The Duchess, so charming, does she share your passion for organic farming?"
The musical is the longest-running in the US and is famed for sending up icons of popular culture.
Sunday night's production included a spoof of television chef Nigella Lawson, as well as red soldiers marching beneath West End posters.
George Schultz - who was appointed as Secretary of State in 1982 by Ronald Reagan - was a surprise addition to the show.
He said it was an "amazing honour" to have the royal couple in the audience.
"I have found that almost without exception [the British] are intelligent, not just smart," he said.
"They have a realisation of things... I have found if you listen to them you actually learn something and I listened a lot."
After a finale - in which Snow White's 5ft hat opened to reveal Charles and Camilla waving from Buckingham Palace - the royal couple joined a standing ovation.
Camilla wore an Alice Temperley skirt and a jacket by Edina Ronay
The duchess, wearing an embroidered red skirt and a black velvet jacket, told the cast: "You did marvellously, well done."
Earlier on Sunday, Prince Charles and Camilla joined a service in a village chapel in California.
The couple sang hymns and said prayers at the Episcopalian St Columba's parish church, Inverness, near San Francisco.
On Monday, they will visit children growing and cooking food at an "edible school yard" in Berkeley, near San Francisco.
Prince Charles will speak at a seminar on environmental issues and he and Camilla will attend a black-tie dinner at the city's de Young Museum.
The couple's tour of the US has so far included a visit to Ground Zero in New York, a visit to people affected by Hurricane Katrina in New Orleans and a tour of a farmers' market north of San Francisco.