Let's apply some common sense here, shall we? First of all, I cannot believe that it is illegal in any state to carry alcohol anywhere in your vehicle if the seal is unbroken. Otherwise, how do you get it home from the store (not all vehicles have a trunk)?
As for RV's, most states look at the cab area and the house area differently. Some states actually allow passengers in the house area to drink while the RV is in motion, others do not. But as for transporting (not actively drinking while in motion), let's once again apply some common sense. An alcohol container that has been opened (think hard liquor, wine, etc) can obviously be legally carried in the house portion of an RV while in motion. Unless proven otherwise, I do not believe that any state would require you to finish (or dump) expensive liquor every time you moved your RV.