Stembolt Countries aren't responsible for what leaves them - Canada and CBSA are responsible for the ridiculous amount of guns, cocaine, crack, and meth that make it into Canada from the US - and they have failed pretty bad at that (and we really should work harder on fixing that and that's why we're willing to spend some $ on the border anyway) -- US CBP is responsible for what is southbound - 42 pounds of fentanyl and 24000 illegal immigrants on the northern border (less than 1% of what they are responsible for missing at the southern border) - no country in the world is responsible for what leaves - we're not jails.
In the meantime the US can "claim" a win for what Canada had already announced it was going to do for the border back in December and they just never paid attention.
And along the way - there's still a lot of angry and hurt Canadians who will likely never buy direct from the US again after this stunt. Stores are going to continue to push the Made in Canada goods, distributors and suppliers are going to be looking for new non-US sources for imported goods so they aren't subject to the whims of an unstable trading partner, grocery stores will be in no hurry to return US goods to the shelves, and Canadian manufacturers are going to continue to look for new outlets and customers to market their wares to that don't have to be paranoid every 30 days for the next 4 years might be the end of their business.