There is a lot of affordable housing; it's just that no one wants to live there for reasons such as work, location, crime, etc. Sure, there is no affordable housing in places like NYC, because too many people want or need to live there.
A quick search on realtor.com for a place like Cleveland. Plenty of houses for 150k.
Yeah, the problem is that if housing is cheap, chances are you can't afford it unless you have an independent income stream (say retirement). And those who benefit from it usually prefer more expensive areas and/or have a need for more premium services like specialist hospitals in the area because they are old.
A quick search on realtor.com for a place like Cleveland. Plenty of houses for 150k.