The US State Department has declined to detail whether gun smuggling is part of the Vice President's agenda and referred the question to the White House. CNN has reached out to VP Harris' office and is waiting for a response.

A spokesperson for the State Department however did tell CNN the Department is committed to working with Mexico to reduce the amount of illicit firearms, weapons parts, and ammunition crossing the US-Mexico border. In particular, the US provides training and equipment to the Mexican government and to the Mexican customs agency.

The problem no one wants to talk about

Experts say policymakers' discussion of the migration crisis often overlooks the source of the weapons exacerbating it.

"It's pathetic frankly how little attention is spent on this," says Adam Isacson, Director for Defense Oversight at the Washington Office for Latin America, a research and advocacy organization based in the US.

"You end up banging your head on the same barriers over and over again: it's like Groundhog Day... It's an issue that everyone knows it's there, but there's no action on either side," Isacson told CNN.

Isacson believes that the particularly fraught narrative around the issue of gun control in the United States -- often fiercely debated among party lines -- is one of the main reasons why leaders spend little time on the issue of guns being trafficked abroad.

Ioan Grillo, the author of Blood Gun Money -- How America Arms Gangs and Cartels, echoes Isacson: "It's kind of mind blowing to me that it is an enormous quantity of firearms, year after year from the United States to Mexico and so much violence happening in Mexico, and it's frustrating that concrete actions are not taking place."

But if Calderon hoped to gain some momentum on this issue with his giant signpost, the tragic results of one such US attempt likely turned American politicians away from trying to tackle guns, Grillo said.

"Fast and Furious was just a disastrous operation, and one of its casualties was knocking the gun trafficking issue off the agenda," said Grillo pointing at the little progress or even discussion of it among US policymakers in the last ten years.

But now could be a time for change. The Biden presidency and a Congress under Democratic control have revitalized the gun debate in the US, which has potential for further consequences in Mexico and Central America.

"I see a huge window of opportunity on the guns issue: this administration has signaled they want to tackle this, and of course they are looking at it as the issue of guns domestically, but these two issues, gun control and gun smuggling, are linked" says Grillo.