US President Donald Trump has sparked uproar over his targeting of top American museums for their focus on subjects including "how bad slavery was"— his latest attack on cultural institutions in a country that fought a civil war over the issue.

"The Museums throughout Washington, but all over the Country are, essentially, the last remaining segment of 'WOKE'," Trump wrote in the Truth Social post on Tuesday, using his shorthand for leftist social justice movements.

"The Smithsonian is OUT OF CONTROL, where everything discussed is how horrible our Country is, how bad Slavery was, and how unaccomplished the downtrodden have been — Nothing about Success, nothing about Brightness, nothing about the Future," Trump added.

He was referring to the Smithsonian Institution, an independent organisation that operates 17 museums, galleries and a zoo located across the country — principally centered on the National Mall in Washington, D.C — which receives public funding, and which he has previously accused of espousing a "corrosive ideology."

"Now museums are being targeted because they speak too openly about the horrors of slavery," wrote prominent civil rights attorney Ben Crump on X in response to Trump's post.

"If telling the truth about slavery makes a museum 'too woke,' then the problem isn't the history, it's the people who want to erase it," he continued.

Trump also suggested he will pressure the Smithsonian Institution to accept his demands, just like he did with colleges and universities by threatening to cut federal funding.

"I have instructed my attorneys to go through the Museums, and start the exact same process that has been done with Colleges and Universities where tremendous progress has been made," Trump said.

'He's cool with the Holocaust Museum'

The translatlantic slave trade from Africa to the Americas spanned three centuries, and has been referred to as the United States' "original sin."

From roughly 1526 to 1867, the slave trade saw approximately 10.7 million of 12.5 million captured Africans arrive in the Americas.

The transatlantic slave trade likely incurred the greatest loss of human life among all long-distance global migrations, with over two million Africans dying during the journey to the Americas, known as the Middle Passage.

The country's South fought to maintain slavery in the 1861-1865 Civil War, but lost.

Since then African Americans have fought for their civil rights, including in the Black Lives Matter protests of 2020, which forced a new national reckoning on the darker parts of US history.

Some critics deemed Trump's attack on museums selective.

"Trump has an issue with slavery being displayed in the African American History Museum, but he's cool with the Holocaust Museum! Everything is WOKE except when it applies to one particular group," podcaster Sabby Sabs wrote on X.

'Spend more time in a museum'

Others rejected Trump's remarks as "outrageous and un-American."

"If Trump thinks slavery wasn't bad, he clearly needs to spend more time in a museum," Representative Jim McGovern of Massachusetts wrote on X.

"Anyone who thinks there's ANYTHING GOOD about enslaving human beings has no business running ANY country…much less the world’s most influential democracy. Outrageous and un-American."

For months now, Trump has disparaged cultural institutions, which have worked to bring more diversity to exhibits and programming in recent years, highlighting women, people of color and queer culture.

Last week, the White House posted a letter to its website saying the administration plans to target eight major museums for "comprehensive internal review" in an effort to "celebrate American exceptionalism" and "remove divisive or partisan narratives."

The targeted institutions include the National Museum of American History, the National Museum of African American History and Culture, and the National Museum of the American Indian, the letter said.

In 2017, during his first term, Trump visited the National Museum of African American History — which opened the year before and which depicts the slave trade, among other historic subjects.

"This museum is a beautiful tribute to so many American heroes," Trump said after his tour, according to US media reports from the time. "It's amazing to see."

"Trump is attacking the Smithsonian museum, saying there's too much focus on 'how bad slavery was.' Authoritarians know that if they can convince us our country has never been wrong, they can make us believe our ruler is always right," asserted Berkeley professor Robert Reich.

"Be warned."