If I had to guess, it's the fact that Russian spacecraft tend to land on the ground, and typically fire a rocket burst right before landing to slow down even more. It's the equivalent of getting kicked in the ass by a rocket-powered donkey, twice.

American craft land in the water, which is much more forgiving to begin with, and I don't think they fire rockets before hitting the surface.

(Although, I'd love to hear more about the other design differences.)