Maybe it isn't happening in those places, but here in KC there's a lot of apartment construction going on. Seemed to be same out in Colorado. Of course, they are all billed as "luxury apartments", but it's in increase in housing space none the less. I mostly chalk it up to young people being generally fiscally unable to enter the single family home market until later in life.
Also, as zahc noted, shanty towns and the like isn't new to america from a longer term perspective. I sometimes wonder if we really just had an exceptional period post war. The rest of the world's infrastructure and manufacturing capacity had been severely degraded by war, but in the mainland US Americans had been building out industrial capacity for the war effort at a blistering pace. Post war foreign markets needed everything, and the US was in the position to provide it with oodles of industrial capitol now idle. Lots of jobs offered low unemployment and a high standard of living.
All of that started to buckle as decades passed and other countries started coming online. India, China, Mexico, etc were able to undercut US production costs by paying it's-a-lot-better-than-substance-farming wages, but no where near what US workers demanded.
And so, the post war boom over, we are gliding back towards the normal state of affairs.
