Seems like the direct translation is 'farmhouse' because the word is only talking about the house itself, rather than a ranch/vineyard/farm. Obviously the size can vary, but descriptively, it would always still be a farmhouse (as opposed to a barn, granary, or other farming structure). In California vineyards, you wouldn't really have any association with the house (where people live) on the property, only the winery (where the grapes are processed). Country estate makes some sense, but an estate is usually a bit more than just a house and more of a compound of structures.

a country estate