US tow safety prioritizes a naturally safe dynamic situation so that more people can pull at freeway speeds with less likelihood of incident. There is no doubt that using this method results in an inherently safer tow situation as it relates to vehicle dynamics.
UK tow safety allows for the possibility to carry more weight, but erring on the side of caution with far less safety margin in respect to the physics.
Bottom line - Can a tow vehicle pull a heavier trailer there than is rated for here in the US? Yes, with some provisions:
1. The closer the trailer weight gets to the vehicle weight the slower you will need to drive.
2. DO NOT exceed 65 mph with a tongue weight in the 4-7% range, this is a guaranteed way to sway and 65 is the max, go slower in regards to #1.
3. None of this takes into account crosswinds, cooling systems, hp, or braking effectiveness (or legality).
Moral of the story
Europeans! Be proud that you can pull that huge caravan with your tiny car.
Americans! Be proud you can pull more weight in total and with a greater degree of safety and at higher speeds than our Euro friends.