Hundreds gathered in downtown Seattle to condemn government violence against civilians and voice concerns over US involvement in the conflict.
Large crowds also assembled in Washington D.C., New York, Chicago, and Los Angeles, denouncing American military engagement in the greater Middle East.
Many participants stressed they were not “pro-Iran” but rather opposed to further government involvement in foreign wars.
A University of Maryland poll showed only 21 percent of Americans surveyed supported a war with Iran, with an overwhelming majority against it.
Critics pointed to President Donald Trump's 2024 campaign pledge of “No New War”, with many supporters expressing feelings of betrayal over the unauthorized strikes.
Outrage centered on the actions as a violation of the US Constitution, which assigns the power to declare war to Congress.
In the past week, Republicans in Congress blocked a Democratic bill intended to restrict the president's authority to launch such military operations.
Separately, around 20 people from the Democratic Solidarity of Iranians group staged a snap protest outside the United States Consulate in North Sydney on March 6.
Participants chanted “No war on Iran”, “Down with Trump”, and “Stop the US-Israel war on Iran”.
Speakers urged passers-by not to let “global warmongers”, “war hawks” decide Iran's future.
They called for an immediate ceasefire, arguing that military aggression would not benefit Iran.
The Sydney demonstration was part of a broader series of actions by Iranian expatriates and anti-war groups urging the Australian government to withdraw support for the US and Israeli operations.
Additional protests took place in other locations worldwide, including Berlin, Germany; Saana, Yemen; Beirut, Lebanon; Baghdad, Iraq; and Manchester, United Kingdom.