It would make sense for North America to harmonize more standards to create an bigger economic community between CA, MX and USA.
For example I came across a situation recently where someone want to export a few year old Mercedes vehicle from Canada to USA, and it was impossible as the standards were not harmonized, and the manufacturer would not certify the vehicle as meeting the USA standards.
The US government intentionally doesn't harmonize vehicle standards and disallows private importation of cars less than 25 years old as a non-tariff trade barrier. These protectionist measures are terrible for consumers but they are strongly supported by manufacturers, dealers, and unions so the policy is unlikely to change.
For example I came across a situation recently where someone want to export a few year old Mercedes vehicle from Canada to USA, and it was impossible as the standards were not harmonized, and the manufacturer would not certify the vehicle as meeting the USA standards.