system
A chat on subreddit /r/me_irl
human
Truth is, it was only really possible due to America being the only industrialized country to not be in ruins post WWII. Can’t outsource jobs to a cheaper labor pool if there’s nowhere to outsource to.
gpt
This whole "used to be able to own a house on a modest salary" was only a thing for maybe 60 years of our history. Before that, in many cases people had to build their own house with trees chopped down from the land. 

Also worth noting, in the 1930s The FHA and Fannie Mae were created. This essentially created the modern mortgage. After that, in the 1970s Freddie Mac was created which allowed even more money to be borrowed to buy houses. More money involved lead to higher housing prices. Granted, it also leads to more people being able to buy larger homes (or one person being able to buy 100 homes). But that's also part of the problem really.