As I recall....
I have a '92 34' Classic Linited, so not your exact trailer, but as I recall the underside of mine had/ has a similar 'smush' around that area. In fact, as I recall there is an access panel in that area - perhaps that is part of what is 'smushed' in your photo?
As the previous reply said, if there is no leaking from the tanks that the 'box' surrounds, then patch it to prevent debris, vermin, spiders, etc.... from getting inside, and GO CAMPING!!!!!
You're gonna LOVE having that AirStream!!!! Or, if not that one, then keep lookin' .....!!!!! There is one out there for you....
All the best,