The Duchess of Sussex has issued a personal message about the impact of George Floyd's death in the United States, saying his life "mattered".
Addressing students graduating from her former school in Los Angeles, Meghan said the events had been "devastating".
She also recalled living through race riots in 1992 and spoke of her regret that nothing appeared to have changed.
In her video message, Meghan called on young people and students at the school to come together to rebuild society.
A wave of anti-racism protests have been triggered by the death of African-American Mr Floyd in police custody in Minneapolis on 25 May.
Four officers have been charged in relation to his death.
Anger has since spread to other parts of the world, including the UK, where thousands of people joined a protest in London on Wednesday organised by campaign group Black Lives Matter.
The sister of black teenager Anthony Walker, who was murdered by two men in a racially-motivated attack in Merseyside in 2005, called for an "ongoing revolution" following the demonstrations - to break down institutional racism in society.
Dominique Walker, vice chair of the Anthony Walker Foundation set up after her brother's murder, told BBC Breakfast that police reform in the UK "has to be taken further".
"There has to be that definitive work that works to break down institutional racism," she said.
In the video of her virtual address to Immaculate Heart High School, the duchess said she was "nervous" about addressing graduates and speaking about events of the previous weeks.
But she said that she "realised the only wrong thing to say is nothing because George Floyd's life mattered", before referring to other African-Americans who died in police shootings in the US in recent years.
In the video, which was first reported by the African-American female magazine Essence, Meghan also gave a heartfelt apology to the graduating students "that we have not gotten the world to the place that you deserve it to be".
She told the all-girls school: "I wasn't sure what I could say to you. I wanted to say the right thing and I was really nervous that I wouldn't or it would get picked apart, and I realised the only wrong thing to say is to say nothing - because George Floyd's life mattered and Breonna Taylor's life mattered and Philando Castile's life mattered and Tamir Rice's life mattered.
"And so did so many other people whose names we know and whose names we do not know."
She then shared her memories of living in the city through race riots in 1992, after police officers were filmed violently beating Rodney King.
The duchess said: "I was 11 or 12 years old and it was the LA riots, which was also triggered by a senseless act of racism.
"I remember the curfew and I remember rushing back home, and on that drive home, seeing ash fall from the sky, and smelling the smoke and seeing the smoke billow out of buildings.
"I remember seeing men in the back of a van just holding guns and rifles.
"I remember pulling up the house and seeing the tree, that had always been there, completely charred. And those memories don't go away."
More on George Floyd's death
Meghan said she could not imagine that the students "would have to have a different version of that same type of experience".
"That's something you should have an understanding of, but an understanding... as a history lesson not as your reality," she said.
"So I'm sorry that in a way we have not gotten the world to the place that you deserve it to be."
She went on to highlight that people are "standing in solidarity" despite the unrest, and appealed to young people to "be part of this movement".
The duchess said: "I know that this is not the graduation that you envisioned [...] but I also know that there is a way to reframe this for you, and to not see this as the end of something.
"But instead to see this as the beginning of you harnessing all of the work, all of the values, all of the skills that you have embodied over the last four years.
"Now all of that work gets activated, now you get to be part of rebuilding."
She added: "We are going to rebuild and rebuild and rebuild until it is rebuilt, because when the foundation is broken, so are we."
In the US, protests began in Minneapolis where Mr Floyd died, and quickly spread across the country.
Demonstrations have taken place in areas including New York, Los Angeles, Miami, Washington DC, South Carolina and Houston.
Some have included clashes between police and protesters, including the use of tear gas and rubber bullets by officers.
US president Donald Trump has pressed state governors to take a more forceful approach against protesters.
The Duke and Duchess of Sussex are now living in Los Angeles with their one-year-old son Archie, after stepping back as working members of the Royal Family.