"I'm Jewish, so I grew up with a great awareness of fascism," she told AFP. "And it has just gotten uglier and uglier" since Trump returned to the White House.
"He acts like he's the vice president," said New York protester Eva Mueller. "He's dismantling, actively, our government, he's dismantling our democracy."
The protest was organized by the environmental activist group Planet Over Profit, which argues "stopping Musk will help save lives and protect our democracy."
In Washington's posh Georgetown neighborhood, some 150 people gathered in a festive mood on an unseasonably warm day, dancing and cheering as passing cars honked.
Protests also took place in Florida, Massachusetts and California, and in European cities such as London, Berlin and Paris.
A small group of Americans held signs outside a Tesla dealership in the French capital, including one that read "Send Musk to Mars now."
Musk and Trump "are destroying our democracy, not obeying the basic rules of our country, and firing people at agencies that do very important work," said Raf, 59, a Paris protester who did not wish to give his last name.
Asked for reaction to the protests, Tesla did not immediately respond.
Acts of vandalism against Tesla vehicles, dealerships and other facilities have spread for weeks, in protest both against Musk's ruthless job-cutting work, and what has been seen as his unwelcome interference in politics.
US Attorney General Pam Bondi has denounced the attacks on Tesla as "domestic terrorism."
