Some homeless people can't be helped since they have mental illnesses and break away from hospitals (USA has 70 times more people and homeless people are concentrating themselves in population hubs - that could make the problem more visible), and so on.
Let's not assume things without proper analysis.
When countries become rich (it's not just America), people lose their connection with poverty and start to blame poor people for being poor. This lets them justify voting against social security programmes because they believe "it will never happen to me, I'm not the kind of person who becomes poor".
Maybe they're voting against it because while they're not poor, they still don't have more than enough - you can solve that by funding it through a progressive tax, but that makes it unfair in the views of many people.
Walking around San Francisco you would get the impression that most homeless people are mentally ill, but you'd be missing all the people sleeping away from busy streets, in tents, in their cars, squatting in unused buildings, couch surfing between friends, etc.
What happens when bank defaults? You become homeless!
It’s a win-win (for the bank).
On a more serious note: a society which has homeless ppl, in 2018, cannot be considered “civilized”.