Slogans were shouted and American and Israeli flags burned in protests in three major Iraqi cities following a call from a former leader of an anti-U.S. militia.
The U.S., Britain and France carried out airstrikes against chemical research, storage and military facilities in Syria following a suspected chemical weapons attack.
The latest action in Syria — which comes shortly after the president said he wanted to withdraw U.S. troops from the country — illustrates the competing impulses that drive his foreign policy.
The military strikes were ordered by President Trump in response to an alleged chemical weapons attack on April 7 by the regime of Syrian President Bashar Assad on its citizens.
A team from the Organization for the Prohibition of Chemical Weapons plans to begin investigating the attack in Douma by Saturday. U.S. Defense Secretary Jim Mattis called the attack "inexcusable."
President Trump had a ready retort to a Russian threat to shoot down any U.S. missiles in Syria: "Get ready Russia, because they will be coming, nice and new and 'smart!'"
Evidence presented in a U.S. federal court claims that the 56-year-old American was intentionally targeted in a rocket attack by Syrian regime forces in 2012. Her family is suing the country.
Meanwhile, President Trump is weighing a possible military response. On Monday, he said "nothing is off the table" and has vowed to respond "forcefully."
Press secretary Sarah Sanders said Trump will remain in the U.S. to oversee the American response to Syria and to "monitor developments around the world."