Americans generally hate station wagons so, more often than not, car companies do not bring them here - they just offer crossovers instead. The Mercedes E-Class is one of the few sedans you can still purchase in the USA in estate form. Mercedes has never sold many of them, but they do have a loyal, affluent niche of customers (particularly in the Northeastern United States, especially New England) who deeply appreciate the model. Credit to Mercedes for staying loyal to that demographic and ensuring that they'll still have at least one solid estate option on the market.
Those Americans who aren't terribly interested in the E-Class and still want a true estate have few options. Audi has quit offering the A4 and A6 Avants, but will still sell you an A4 Allroad (essentially an A4 Avant with some extra cladding and a touch of extra height to make it look more crossover-ish). BMW steadfastly continues to offer the 3-Series wagon in the States, despite it accounting for such a small percentage of all 3-Series sales. The Subaru Outback is still (sort of) a Legacy station wagon. Volvo will sell you a V60 and VW can offer the Golf Sportwagen.
The E-Class is probably the best of the lot, IMO.