To put it bluntly, what utter bull excrement.

Driving down years ago is no indication that it is safe to do so today.

Canadians are warned: "Avoid non-essential travel to the border areas. Avoid travel by land to or through northern border states. Travellers are advised against crossing Mexico’s northern border by land and should do so only if it is absolutely necessary, after making appropriate arrangements to ensure their personal safety."

In addition, your quoted route down to Cancun goes through Tamaulipas state where you are suggesting an overnight in Tampico! Both the US and Canada caution "against all non essential travel" to this area, and specifically mention things like heavily armed gangs, illegal road blocks and kidnappings.

State departments don't make decisions lightly, and you would be incredibly foolish to ignore their advice.