VANCOUVER, British Columbia — Every time there’s another mass shooting in America — and there have been many relative to other nations — the country spends a few days trying to pinpoint the root cause in a futile attempt to prevent it from happening again. None of the explanations offered thus far adequately explain why this keeps happening.

Sure, America has easy access to firearms, but so does Switzerland, and mass shootings there are virtually unheard of. Nor is America the only country on earth grappling with racism, or mental illness, or social alienation, or violent video games, or online forums that promote extremism. None are unique to America, yet mass shootings are far more common in the U.S. than anywhere else. There’s something else going on here — but what, exactly?

Both of the recent massacres, only hours apart in El Paso, Texas, and Dayton, Ohio, were perpetrated by young white men in their early 20s. That they had polar-opposite ideologies complicates the search for easy explanations.

Based on an online manifesto attributed to the El Paso gunman, he was a Donald Trump supporter and an anti-immigrant nativist. Meanwhile, the Dayton gunman’s social media accounts revealed enthusiastic support for socialism and an avid dislike of Trump. The two shooters do, however, share an overlooked common thread that transcends their respective ideologies. It’s one that’s shared by jihadists and yeehawdists alike: vigilantism, or the notion of taking the law into one’s own hands.

Vigilantism is a concept that has been promoted, if not glorified, in America for decades. It’s a twisted interpretation of free-market, limited-government self-sufficiency, except it goes to the extreme of violence.

Violent vigilantism has been endorsed by the U.S. government itself, which has frequently given its blessing to private mercenary actions on foreign soil, most notably in the Middle East. Cronies from the military-industrial complex left government service because they had found a way to funnel the defense budget into their own pockets. Their business plan can be boiled down to hiring guys to kill people for money. Once the government literally gives civilians the license to kill and loses its longstanding monopoly on deadly force, it effectively authorizes vigilantism. It’s that critical element of U.S. culture — the outsourcing of violence to nonstate actors — that sets America apart from other nations.

The shooting at the Walmart in El Paso that killed 22 people and injured dozens of others took place only a stone’s throw away from a recently erected monument to vigilantism. A group of self-described “patriots” grew tired of waiting for Trump to build his promised border wall, so they raised over $20 million to build their own wall on the border with Mexico. They amped up the rhetoric about invasion and the danger of migrants on social media and in press releases, and they erected a piece of wall on private property.

The organization spearheading the independently funded barrier, We Build the Wall Inc., has an advisory board featuring professional disinformation peddlers and mercenaries. Their message was that their efforts were necessary because the government was inept. For this group, the end justified the means — laws be damned. After months of this vigilante rhetoric in El Paso, a young man wrote a manifesto about how government is useless in response to migrants and then drove across Texas to shoot up a Walmart in the same town.

How much of a slippery slope is it from ignoring the vigilante actions of one group to creating a climate in which other vigilantes feel empowered to act lawlessly?

There’s a certain romanticism about vigilantism in America, often depicted in Hollywood films. Perhaps it’s because vigilantism is often confused with ingenuity, particularly when government is perceived to have failed. It’s only when the results are as deadly as they were last weekend that people denounce vigilantism en masse.

This phenomenon is uniquely American. In France, a group of young people who allegedly took it upon themselves to block migrants from crossing into France from the Italian Alps last year now face six-month prison sentences. What about activists who do the same in America at the Mexican border?

The American government divested itself of its exclusive monopoly on violence when it blessed foreign mercenary action. Now, politicians on both sides of the aisle are doing little or nothing to denounce domestic mercenary action furthering ideological causes favorable to them. Democrats and Republicans alike are responsible for turning a blind eye to the vigilantism that supports their causes. The result is the empowerment of radicals on both sides.

Rachel Marsden is a columnist, political strategist and host of an independently produced French-language program that airs on Sputnik France. Her website can be found at www.rachelmarsden.com.