It is amazing that despite the agitation for war in all US media (some left, center and most right), you have to read the full text of articles in the New York Times to realize that in fact the US government and the British government does not have incontrovertible evidence. Look at this:
1) here is the New York Times' own evidence: "“a New York Times review of more than 20 videos of its aftermath”."
2) "“International investigators have yet to visit the site to determine whether chemicals were used”."
3) "“British Cabinet had “agreed that...and it is highly likely that the regime is responsible for Saturday’s attack,” Downing Street said in a statement.”"
4) "“The Trump administration has not yet confirmed the use of chemical weapons by the Syrian regime.”"
5) "“[Mattis] also underscored the importance of a preponderance of evidence linking Mr. Assad to Saturday’s suspected chemical weapons attack.”"
1) here is the New York Times' own evidence: "“a New York Times review of more than 20 videos of its aftermath”."
2) "“International investigators have yet to visit the site to determine whether chemicals were used”."
3) "“British Cabinet had “agreed that...and it is highly likely that the regime is responsible for Saturday’s attack,” Downing Street said in a statement.”"
4) "“The Trump administration has not yet confirmed the use of chemical weapons by the Syrian regime.”"
5) "“[Mattis] also underscored the importance of a preponderance of evidence linking Mr. Assad to Saturday’s suspected chemical weapons attack.”"