• Societally and culturally produce so few individuals who would behave the way America's most problematic homeless do that direct 1on1 intervention is feasible. There are school districts in the US where the truancy rate exceeds 70%. There are other countries where this is not the case. Switzerland and Norway come to mind.
• Involuntarily commit or arrest individuals who are mentally unfit to function in normal society. Institutionalization, basically. China and Russia come to mind.
If there was a silver bullet which was politically acceptable to "solve" America's homeless problem I ensure you, folks in California would have tried it.