porous border with Mexico? and by the time it arrived it was too late.

if you say Mexico is in your definition of North America then it should include all of central america, almost all these countries have a lot of land-based trade.

In Canada we have not had any cases related to truckers, but there's a lot of them who have to do the cross-border route, as well as people who commute daily across the border. heck in Canada and the US there are a few spots where crossing the border is necessity -- the only school is in the other country, nearest hospital, the local library, a popular golf course, etc.

or places like point roberts, extremely small but extremely isolated, or Hyder, Alaska.