Meghan is the first American to marry into the royal family since Wallis Simpson in 1937

Meghan Markle is the first American to marry into the British royal family since Wallis Simpson in 1937 — and since her wedding to Prince Harry in May, there have been tensions that some insiders blame on a culture clash.

Veteran royal aides “might not be used to the ‘say-it-as-you-see-it’ American mentality,” a palace insider tells PEOPLE in this week’s cover story.

Meghan, 37, has yet to announce which patronages she will back as a member of the royal family, but it’s clear she has ambitions to advance education and empowerment for women and young girls around the world. Her first solo project as the Duchess of Sussex – a cookbook launched to support a community kitchen – spearheaded that cause.

“The palace is a magical place, and it is also a place where all you hear is ‘no, no, no,’ ” a source in royal circles says of the confining rules that govern royal life.

Credit: Samir Hussein/WireImage; Karwai Tang/WireImage
The Queen Attends A Service At Westminster Abbey Marking The Centenary Of WW1 Armistice
Meghan Markle and Kate Middleton
| Credit: Paul Grover- WPA Pool/Getty

Adds a source close to the family: “The most difficult job in the royal family is to work with Meghan’s ambitions and make them realizable. She will get frustrated if she is told, ‘You can’t do this or can’t do that.’ ”

Royal Christmas cards
Credit: Matt Porteous

Kate Middleton, on the other hand, “has maneuvered herself in a different way, but she is still strong.”

Prince William‘s wife, 36, grew up in the English countryside with entrepreneur parents Carole and Mike Middleton. In addition to knowing her place as the future Queen, she has immersed herself into life as a mother to the couple’s three children: Prince George, 5, Princess Charlotte, 3, and Prince Louis, 8 months.

William and Kate “have created their own nest, and they are confident in what they’re doing,” says the insider.