Exactly. This makes the comparison kind of invalid. I've owned a Grand Cherokee before and while they can tow, the rear suspension is just too soft stock to do any kind of serious towing. Not to mention that with the V-8, the cooling system is barely adequate.
Another reason why the car is not rated to tow here in the U.S. is probably to do with the EPA. New vehicles must meet emmissions requirements while they tow. For example, this is why my old 4 cylinder Chevy Colorado was only rated to tow 2,000 pounds, but the 5 cylinder Colorado was rated to tow 3,500 pounds. The ONLY difference between the 2 vehicles was the motor. The 4 cylinder truck could tow 3500 pounds, but it would not meet the EPA requirements while doing so, so it had to be rated to tow less.