I'm now very familiar with stink bugs since they ruined a nice crop of tomatoes I had in the backyard. They pierce the skin of the tomato and suck the juice out. Everywhere they feed ends up leaving a dead spot. They ended up ruining every last tomato I had that year.
Washing the trailer is a very good idea. Soapy solutions will trap and kill them. They breathe through pores in their shell. The soap cuts through the waxy protective coating and clogs the pores. However, they're very good at finding hiding spots and can keep a pretty good grip to the surface they're on, so there's a good chance that some won't just blow away while going down the road. I doubt that RVers are mostly responsible for the local invasion. They're fairly strong fliers with no natural enemies here in America. They have enemies, but non that are naturally attracted or targets them. With those conditions they can spread pretty quickly. I have to give you kudos for at least not wanted to add to the problem.