I am from a "poor country in Eastern Europe". I'm not sure how you think homeless is dealt with here, but it is nothing that left-wing US liberal would find palatable I assure you.
I'm from Poland. Homelessness is not solved maybe, but it's nowhere near to the level of US.
The solution seems to be public healthcare, education, transport, safety net and cheap housing.
Addiction and mental illness are excuses. Eastern Europe has more mental ilness (generational trauma from WW2 is still alive) and alcoholism than US and yet it has less homeless people.
In early 90s my parents were earning 20 USD per month each. It was about average. There were still almost no homeless people.
It is not "solved", it is marginalized because homeless people are much less tolerated compared to, say, California. In very simple terms a homeless person getting caught shitting on someones porch in Eastern Europe gets punched in the face and kicked out. And no way homeless would be allowed to just squat some park or square with tent encampment in a major city here.
Overall, I don't see neither US nor Poland as a big outliers by looking at the stats[0], it just seems like some specific places (SF) made homeless population a highly-visible nuisance by feel-good unrealistic policies that can't possible work.
