From San Francisco to NY, people spoke out against President Donald Trump's show of power.
But the strike could set in motion events that force Trump to take a more active role on the world stage, experts said, while others suggested the chemical weapons attack might have changed Trump's outlook on the role the United States should play.
Peskov, Putin's spokesman, said on Monday that the USA strikes had shown Washington's total unwillingness to cooperate on Syria.
"We deplore Russia's continued defence of the Assad regime even after the chemical weapons attack on innocent civilians".
"Using a deadly nerve agent, Assad choked out the lives of helpless men, women and children".
Those include alleged Russian interference in the 2016 USA presidential election, Washington's accusation that Russia is violating an important arms control treaty, and trying to bridge differences on how to conduct the fight against Islamic State. Shortly afterward, officials say the hospital was targeted.
Washington has blamed the Syrian government for the attack on Tuesday. He didn't give precise numbers.
On Friday, senior US military officials were looking more closely at possible Russian involvement in the poison attack.
The White House is circulating a letter President Donald Trump sent to the leaders of both houses of Congress explaining his decision to order military strikes on a Syrian air field.
In response, Syria's ally Russian Federation accused the United States of encouraging "terrorists" with unilateral actions.
The United States acted in a dangerously unilateral manner before any global investigation into what happened or offering any solid evidence concerning the suspected use of chemical weapons.
"Either Russia has been complicit or Russia has been simply incompetent in its ability to deliver on its end of the agreement", Tillerson said.
Davis Cup: US wins doubles to stay alive in quarterfinal
Nick Kyrgios has sent Australia through to the Davis Cup semifinals, with an emphatic straight-sets win over American Sam Querrey. They edged out Australians John Peers, ranked third in the world in doubles, and Sam Groth 3-6, 6-3, 6-2, 2-6, 6-3.
The Kremlin said on Monday that U.S. Secretary of State Rex Tillerson will not meet President Vladimir Putin when he visits Moscow on Wednesday, a move that could point to tensions over a U.S. missile attack on a Syrian air base last week. The president did not announce the attacks in advance, though he and other national security officials ratcheted up their warnings to the Syrian government throughout the day Thursday.
The US strikes obliterated substantial portions of Syria's military capacity there.
Johnson said no one could reasonably object to the United Nations resolution, while Downing Street had previously played down the prospect of military action.
Russian foreign minister Sergei Lavrov said the Americans had used a "far-fetched pretext" to justify the attack while the defence ministry in Moscow said it would be helping its Syrian ally strengthen its air defences. "And we believe that the first priority is the defeat of ISIS", Tillerson said in a clip made public on the eve of the Sunday talkshow's air time.
Still, the assault risks plunging America into the middle of Syria's conflict, complicating the safety of the hundreds of USA forces fighting a separate campaign against the Islamic State group in the north of the country.
Iran and Russian Federation are Assad's closest allies and label all opponents of his regime as "terrorists".
Iran says it has military advisers and volunteers in Syria but denies having a conventional force on the ground.
Sources close to Johnson said he would instead "lead efforts to bring together a coalition of support against ongoing Russian activity and the Syrian regime". The goal was to avoid any accident involving Russian forces. "The U.S. strike creates an opportunity for the Russians to get some leverage over Assad if - this is a big if - it looks like the U.S.is going to be more involved and this wasn't just a one-off strike".
A No 10 spokeswoman said: "The UK Government fully supports the United States action, which we believe was an appropriate response to the barbaric chemical weapons attack launched by the Syrian regime, and is meant to deter further attacks". "What America waged in an aggression on Syria is a crossing of red lines".
The world learned of the chemical attack earlier in the week in footage that showed people dying in the streets and bodies of children stacked in piles. After years of calling for al-Assad's removal during former president Barack Obama's tenure, Washington appeared to be stepping back from seeking regime change in Syria in recent weeks.
The show of force in Syria raises legal questions. Trump can't rely on either justification here.
The impact of the strikes was also unclear.