I have wondered if the bull guards I see on 18 wheelers are actually meant to deflect a bull at interstate speeds. I mostly notice them on cattle trucks that are likely to encounter animals at very low speeds. Taking a hit from a 1,000lb animal at 60mph without damage would probably require that the guard be able to bend back a couple of feet and then rebound.
There are so many different RV's out there that making something fit very many even on the same chassis would be challenging so you are probably looking a custom fit. I recently installed a front hitch on my Palazzo with a Freightliner chassis to haul scooters but don't think that I have seen another DP that could use the same design. When you start looking the number of variations in RV's is incredible. I actually did design the front hitch with triple sockets with the thought that I might put some Super Bumpers in it when not hauling the scooters. I have not done that yet. That thought was inspired by backing into a bear-proof trash can on my first outing. As much as it cost to hit a trash can I don't even want to think about repairing the damage from something substantial.
I bet that the Smart Car would do less damage than most of the animals in rgatijnet1's list. It is probably softer.