I don't know why more Americans don't buy wagons. They are extremely useful and you hardly give up anything compared to the same model sedan. I guess people have an image problem with them

Because we have SUVs, they are "image friendly."
I think you are correct in that the wagon's image in the USA is a family vacation-mobile. I really like the looks of the newer Volvo wagons, but I agree with TigerJimmy regarding a used E Class MB. A friend got a really nice, low mileage 2 year old one for less than $40k last year. I'm going that route when the boat and truck are paid for.