I can't say I've done a full study on this, but at least anecdotally, the claim of this article seems over-blown. I'm a software engineer for a large tech company (i.e., I make pretty good money), and I live in a relatively well off part of the US (New Jersey, in the New York suburbs). When I was looking for a house, most houses in our price range had either 1 full bathroom or 1 full bathroom and 1 half bathroom. So even in a pretty well-off situation, it's not automatically the case that you live in a huge house with lots of bath rooms.
To the extent that the claim that American houses have so many bathrooms is true, I'm not sure you can think about American real estate in such a homogenized fashion to assume it is universally true. I think it applies in certain particular circumstances, but is not universal.