Canadians felt good when Trudeau responded to Trump's ban on Syrian refugees by tweeting: "To those fleeing persecution, terror and war, Canadians will welcome you, regardless of your faith. Diversity is our strength. Welcome to Canada." Feeling morally superior to Americans is one of Canadians' favourite pastimes, and in this case it is self-evidently true.
The United States took in 12,587 Syrian refugees last year; Canada, with one-ninth of America's population, accepted almost 40,000. Yet there have been only two lone wolf Islamist attacks in Canada in this century, each killing one person and neither carried out by an immigrant. A non-Muslim crazy has just murdered six Canadian Muslims in Quebec City, but Muslim immigrants pose no appreciable danger to their fellow Canadians.
If Trump's domestic opponents use the Canadian example to discredit Trump's story about the mortal danger posed by Muslim immigrants, the man might claim that lax Canadian immigration policy is a threat to the United States and apply "extreme vetting" measures to Muslim Canadians who want to cross the border.
In reality, there is no significant danger from Muslim immigrants to America either. Most of the 28 major massacres in the United States since 9/11 were carried out by white right-wing extremists, and those that did involve Muslims were almost all committed by native-born Americans.