Aliza Cosgrove, an 18-year-old protester in Seattle, said she would like to see more young people who grew up in the digital age — particularly those who come from privileged backgrounds — demonstrating in public.

“When you go on the internet, you see so many people talking about the world and talking about what’s going on, and they just make jokes or repost something and that’s all they do,” she said. “There’s good in spreading the message on social media, but there’s also direct action in going out and raising your voice.”

Act Now to Stop War and End Racism and Code Pink began calling for nationwide protests on Tuesday, ahead of the drone strike that killed General Suleimani but as tensions were escalating between the United States and Iraq, Mr. Becker said.

Protests were initially planned in 10 to 15 cities and the number grew to 30 by Thursday. When the general was killed near the Baghdad airport early on Friday, the number of participating cities more than doubled, Mr. Becker said.

As of Saturday afternoon, more than 80 protests were organized, Medea Benjamin, a director of Code Pink, said.

She said she had not seen numbers like this since 2003.

“One thing that’s very different this time is that more young people and people of color came out to protest,” Ms. Benjamin added.

Ms. Benjamin said the surge of protesters reflected a momentum and energy that she hoped would be seen and heard by lawmakers.