Canada's Prime Minister Justin Trudeau hugs a resident in La Loche, Saskatchewan, where a 17-year-old was charged with killing four people and wounding seven in a mass shooting. (Jonathan Hayward/Reuters)

The United States is to Canada what Mexico is to the United States: the reason for border trouble. We get illegal immigrants smuggled from Mexico; Canada gets illegal guns smuggled from us.

But who, pray tell, gets the worst of it?

Much is made about the impact of illegal immigration on states along the southern U.S. border. But what about the impact of illegal weapons making their way into the country to our north?

Smuggled firearms from the United States are fueling bloodshed in Canada. A couple of sentences from a story in The Post this week by William Marsden said it all: “Homicides in Toronto spiked to 80 in 2005, from 64 in 2004, and the majority were shooting-related. About 70 percent of the guns used were handguns and automatic weapons smuggled from the United States, police say.”

While the number of shootings has decreased, gun seizures by the Canadian Border Services Agency reportedly are up: 226 illegal weapons were seized in 2012, most of them handguns; there were 316 by 2015.

To be sure, our own gun-violence numbers swamp Canada’s: There were 156 gun-related homicides in Canada in 2014, Marsden reported, compared with 10,945 the same year here. That may be cold comfort to Canadians, who experienced a 16 percent increase in gun-related killings in 2014.

Alarmed by the increased number of high-powered handguns and semiautomatic and automatic weapons in his cities, Canadian Prime Minister Justin Trudeau indicated that he will seek tougher laws that would “get handguns and assault weapons off our streets.”

Folks in our nation’s capital should wish him luck. We know all too well about illegal guns. And we are learning more about what those weapons can do, especially in young, undisciplined hands.

Canada shouldn’t want to witness a development of this kind, though there are indications that youth gangs in the commonwealth up north are getting their hands on guns as well.

To gauge the impact of illegal guns on youth here, I asked the D.C. Office of the Attorney General to total the number of gun-related juvenile cases it prosecuted between Jan. 1 and Nov. 1, 2015.

OAG reported that law enforcement presented 136 cases of juveniles arrested in the District in connection with gun-related offenses for that period.

Each case, the office said, involved at least one gun offense, such as carrying a pistol without a license, possessing an unregistered firearm or unregistered ammunition or at least one offense related to the use or ready availability of a firearm for crimes such as armed robbery, assault with a dangerous weapon or assault with intent to kill while armed.

Of the 136 arrests, the attorney general’s office brought charges in 100. The office said it “no-papered,” or declined to prosecute, 36.

Reasons for no-papered cases, OAG explained, included insufficient evidence, constitutional error by law enforcement, witness noncooperation and a hold on bringing some gun charges in early 2015 because of questions regarding the charges’ validity, given litigation over the District’s gun laws.

Again, these juvenile gun-related statistics are limited to arrests. The count of unsolved gun-related cases by juveniles was not readily available.

Canada, faced with the possibility that illegal guns can reach juveniles more easily than legal guns, may take a page from D.C. Attorney General Karl A. Racine’s playbook.

Racine and city agencies have started a program to divert low-risk juvenile offenders out of traditional prosecution into a city-run program known as ACE (Alternatives to the Court Experience). This program is aimed at steering young people away from guns and the juvenile criminal justice system.

A January report from ACE shows significant success, according to the attorney general’s office. Of the 742 youths participating from its inception in June 2014 through 2015, 92 percent had no further involvement in the legal system while in the program. Even after completing the full six-month intervention, 92 percent had not been rearrested.

This kind of program is not a sidebar to the discussion of gun violence or the proliferation of illegal guns in this city, Canada or anywhere else. It is central to the effort to reduce the shootings and the crossfire on our streets.

Meanwhile, our neighbors up north, fearful of the firearms smuggled from the United States, are planning to install devices at border stations to “detect and halt illegal guns.”

Calls to mind the proposed construction of a wall and fence along our southern border to halt illegal immigration from Mexico.

Because it appears we are doing to Canada what Mexico is doing to us.

Read more from Colbert King’s archive.