The royal duo will have plenty to figure out in the coming weeks, but Julie Montagu has proven that a transition between the culture of American and that of the British aristocracy is a possible one.
Montagu grew up in Illinois before marrying Luke Timothy Charles Montagu, Viscount Hinchingbrooke, heir to the Earl of Sandwich -- and relocating to England, indicating that she is well-versed in the cultural differences that Markle, 38, and Harry, 35, will experience.
"I always say whenever you meet an American, you know their life story within 24 hours," Montagu explained to Town & Country. "We're very emotionally open, which I think for Harry is actually a really good thing. He'll be able to talk about his feelings, probably more than he was able to talk about over here.
"I wouldn't be surprised if we start to hear a little bit more about how he feels about losing his mother at age 12, and maybe how he and Meghan were treated in the press over here," she added.
Harry and Meghan aren't the only ones that will have to balance cultures, as their son Archie will likely have to pick up on certain English traditions.
"My husband grew up knowing you should be fully dressed for meals, socks and shoes on," Montagu said. "We set the table for breakfast, lunch and dinner. And when I say set the table, I mean set the table. We have placemats, all the cutlery out, the glasses, and we serve everyone as our guests."
Montagu also said she imagines Meghan's American parenting style to be similar to her own, such as saying "I love you" to one another.
"I remember one thing my husband said to me when we were dating is that every time I spoke to my parents, I'd hang up the phone and say, 'I love you, Mom and Dad,'" Montagu remembered. "I'm like, yeah, that's what we do! My kids say 'I love you' all the time, and we hug."
Montagu, also an author, noted that there's a difference in people's outlooks between the two countries as well, which she believes will make for an enjoyable atmosphere for Harry.
"That cheery, optimistic outlook on life is everywhere in America and it's so contagious. I love it," she said. "And my kids always notice how much people greet each other on the street."
Montagu also pointed out one surprising difference between the two cultures: the customer service.
"America has the best customer service in the whole wide world," she told the outlet. "It's three rings on the phone and someone is there on the other end, or you go into a shop and as soon as you walk in, they greet you, and when you leave they say, 'Oh, have a great day!'"
Despite all of the upcoming changes that Meghan and Harry will face, Mongatgu feels optimistic for the couple.
"I feel like he has found somebody that he can be emotionally open with and I think that's a really good thing," she said. "Family becomes the most important thing."