Expressing "deep concern" over the circumstances surrounding the cancellation of the programme on Saturday, the US embassy here alleged a "troubling pattern of impunity" for law violators.
The event, focused on digital security for Jaffna-based journalists, was supported by the US government.
"We have raised our concerns with the Government of Sri Lanka and the Sri Lankan Embassy in Washington, and strongly urged the Government to take immediate steps to ensure the protection of fundamental rights for journalists and for all Sri Lankans," a statement released by the US embassy said.
"These events continue a troubling pattern of impunity for those who interfere with both freedom of speech and freedom of assembly in Sri Lanka," the statement added.
The Free Media Movement (FMM) said a workshop organised by them for journalists from northern Jaffna peninsula, a former conflict zone, was abandoned after threats by pro-government groups.