"Have you met the Queen?"
When I was New York correspondent for the Daily Telegraph>, that was the question I was asked more than any other.
From the coalmines of West Virginia to the ritzy Upper East Side of Manhattan, Americans are obsessed with Her Majesty – almost 250 years after they kicked out her ancestor George III.
But, much as they revere the royal family, the ardently patriotic Americans don't like them interfering with their hallowed politics and constitution.
So they won't take kindly to Prince Harry's unprecedented intervention into American politics this week, just before the Presidential election.
Sitting next to the Duchess of Sussex, broadcasting from their Californian mega-schloss, Harry declared: "As we approach this November, it's vital we reject hate speech, misinformation and online negativity".
You don't have to be a genius to see which Presidential candidate attracts Harry – who doesn't have a vote in America and, by royal convention, has never voted in a British election. The Duchess of Sussex and Donald Trump have recorded their dislike for each other. It's clear Harry was encouraging American voters to back the Democratic candidate, Joe Biden.
"The golden rule for the royal family is that they do not trespass into politics, and most particularly not into party politics," says Hugo Vickers, the biographer of the Queen Mother and the Duchess of Windsor, who gives regular lectures on the royal family in New York, Lexington and Palm Beach. "I wish Prince Harry would cease to be a mouthpiece for his wife."
Americans may be obsessed with the royal family. That's why they invented the Kennedy and the Trump dynasties. But they want to admire royals from afar, sitting on thrones in crowns and tiaras. They don't want to be lectured by them.
"We adore the royal family," says Donna Freed, a writer and native New Yorker, living in London. "We wouldn't want them - let alone pay for them – but we love that you do. It's a real-life Dynasty – great outfits, great gossip – but it's not like we listen to them."
There is also a very real danger in the royal family siding in any political debate. One of the reasons they've survived so long is because they appeal to both sides of the political divide.
That's why it was so controversial when, in the 2014 Scottish independence referendum, David Cameron said the Queen had "purred down the line" when he told her Scotland was remaining part of the Union.
It was controversial, too, when the Queen said, days before the Scottish referendum, that Scots should think "very carefully about the future". That was interpreted by some as political intervention, backing Scots to vote to stay part of the United Kingdom.
Prince Harry should be very careful then about intervening in American or British politics.
"He's just spouting what the Duchess says," Vickers says. "The royal family talking about climate change isn't political. When Prince Charles sees what's going wrong with climate change and pronounces on it, that's fine. But they're careful not to be political about, say, Brexit."
The chances are, though, given the Duchess' increasing political activity, that Prince Harry will continue to be politically outspoken.
"If the Democrats get in, America will go completely woke," says Vickers. "She can make all the woke speeches she likes while he looks after Archie – he's gone from being Captain General of the Royal Marines to a childminder in two easy moves.
"It's all been totally calculated by her. She now has the global recognition she wanted."
In the end, Americans will just ignore Prince Harry, particularly if he's loafing around, dressed in a T-shirt and beanie hat. They like him in full-dress military uniform – but, even then, only to look at him, not to listen to anything the self-confessed non-intellectual might have to say about politics.
If anything, a Prince Harry intervention will only backfire – just like Barack Obama's suggestion in 2016 that Brexit would leave Britain at the "back of the queue" in trade negotiations. British voters ignored the charismatic President – just as American voters were enraged by Hillary Clinton calling them "the deplorables… the racists and the haters" in 2016 and voted for Trump in their millions.
If Prince Harry knows what's good for him – and his popularity on both sides of the pond – he should steer clear of politics.
• Harry Mount is editor of The Oldie.