The difference has to do with culture.
Off shore you have smaller vehicles and they are not into the use of WDH's. That is why the tongue weights are on the light
side. Because they are on the light
side they design their trailers in a way that they can be towed that way.
In NA there is a split culture. The mainstream side use the traditional large heavy vehicle and use a WDH, or just on the ball if the trailer is light
Then there are the lighter vehicle as in cars that the marketing folks here see has non participants in the towing field. So they simply rate them low so folks ignore them and buy the big profit, big heavy vehicles.
Then again you have the specialty group who evaluates lighter vehicles, works with their potential, adds the valued WDH to the mix, and comes up with the ultimate TV's. With that comes economy, stability, and safety.