You seem to be assuming that the differences don't have a rational basis. Cars are generally homologated for a large geographic area, which might include Arizon

You seem to be assuming that the differences don't have a rational basis. Cars are generally homologated for a large geographic area, which might include Arizona even if the car is sold in Canada. Towing limit standards may also be defined differently in law. Hypothetically the regulations might specify that the vehicle must be capable of safely towing the stated load without overheating at X incline at Y speed for Z time at A altitude, be able to stop in B meters, plus C overall safety margin. It's entirely reasonable and rational that the values of X, Y, Z, A, B and C might be different in Europe and North America.