The Duke and Duchess of Sussex visited the Los Angeles National Cemetery to mark the occasion.
They placed flowers picked from their garden at the graves of two Commonwealth soldiers, royal biographer Omid Scobie tweeted.
Harry and Meghan also placed a wreath at an obelisk in the cemetery with a plaque inscribed with the words: “In Memory of the Men Who Offered Their Lives in Deference of Their Country.”
The Duke's message on the wreath read: “To all of those who have served, and are serving. Thank you.”
The images were released by the couple’s office.
But it sparked a huge backlash online, with critics questioning why they didn’t “do it privately” instead of carrying out “stunts”.
Good Morning Britain host Piers Morgan tweeted: "Just outrageous – treating Remembrance Sunday like a PR opportunity, & trying to steal headlines from the real royals doing their duty back home."
One Twitter user responded: “I thought they wanted a quiet private life, and had given up all this sort of stuff!
“Attention seekers, virtue signalling.”
Another social media user sarcastically wrote: “So lucky a photographer was walking past!”
While a third posted: “That’s a stroke of luck, a photographer just happening to be there.”
TalkRadio host Dan Wootton tweeted: “How lucky that a photographer happened to be here to capture this deeply personal moment.”
But supporters of the royal pair leapt to their defence.
One tweeted: "What beautiful photos, and a lovely gesture."
Another said: "They did not let nothing stop them from honouring the fallen soldiers. Thank you for serving from your hearts & with kindness."
And one added: "They found a way they can take part and pay respect."
A source told Harpers Bazaar: "It was important to the duke and duchess to be able to personally recognise Remembrance in their own way, to pay tribute to those who have served and to those who gave their lives."
According to the publication, the cemetery they visited is opposite the Veterans Affairs Greater Los Angeles Health Care System building.
Alvin Ragland, Meghan’s grandfather, used the building after he served in the US Coast Guard.
It follows reports Harry was refused permission for a wreath to be laid at the Cenotaph on his behalf.