Does exceeding manufacturers' tow rating void collision liability insurance?

A 2012 VW Golf is rated to tow 3000 lbs in Europe and 1000 lbs in the USA. Why?

I'd expect that a Golf towing a 1800 lb trailer at 60 mph would be no problem, until I had a wreck and the insurance company tried to deny my claim.

Here's a guy towing an AirStream trailer with a Golf http://forums.tdiclub.com/showthread.php?t=333675 A glider trailer is 40% the weight of the Airstream and low to the ground.

Is the published tow capacity set by the marketing department with 'input' from engineering? The Golf is marketed as a sporty run-around in the USA and a tow rating might hurt that image.

My guess is that VW Golf is probably better for towing than the VW Tiguan despite the ratings. The Golf is 330 lbs lighter than the Tiguan, but it has a lower center of gravity. The 'overhang' from the rear axle to the tow ball is about the same for both cars.

Golf - Curb Weight - 3,074 lbs - Towing Capacity 1000 lbs

Tiguan - Curb Weight 3,404 lbs - Towing Capacity (max braked trailer) 2,200 lbs
The maximum legal towing speed in Europe is 60 mph.