What? Why? Economically possible would mean that our society is not productive enough, that it doesn't have the capacity, to produce small little houses for everyone who wishes one. I doubt that is true in any modern economical system.
America is a big place. There are a lot of places suitable for living out different dreams. Some (many?) dreams are just not conducive to some (many?) situations/locations, others are.
Buying into dreams promoted by the wealthy are expensive. A lot of what we consider normal, even vital, is the result of accepting advertising's message; wasn't long ago such was considered luxurious, even impossible.
Living [sub]urban lifestyles requires reliance upon others for pretty much everything, with many layers of middlemen taking a cut for profit & raising prices; that's not a condemnation, just observation of reality. Shorten the distance & layers between source & use.
Just once I would like the authors of these "it's just not economically possible for X to have Y" to be referring to themselves in group X.
Disproof: For certain possible values of "everyone", the Pauli Exclusion Principle prevents the simultaneous existence of a sufficient number of distinct small houses.
This energy state ain't big enough for the both of us.