How is it not? You have ultra rich living above and driving around people living in tarps on the street just like what you see in corrupted "third world" places around the world. It is so demoralizing living near a homeless encampment and seeing how people live every day for years, and seeing nothing done to improve their situation. No other first world country I know is like that. First world countries have governments that support their citizens even at the lowest rung of the ladder. What we have is a third world oligarchy, where politicians listen to powerful people looking to personally enrich themselves first and foremost, and if something happens to help the common man rather than hurt them it is usually happenstance, or highly diluted from the original aim to the point of being inconsequential. There's only action when there is profit motive. It's corrupt.
Last time I was in France (Lyon, a few years ago), there was quite a number of homeless people camping out in the parks. Is France also a third-world country?
I agree that the homeless situation is bad. I don't think blanket claims that other "first world" countries handle it much better are necessarily true, unfortunately.
One (or a couple of) cities don't represent the whole country, naturally.
These were probably either recent migrants ("refugees" for lack of a better term) or Roma camps (which are not today's problem). They could as well just be homeless, sure (depends on the park, location, etc). Mostly, they are the result of progressive policies gone unchecked as well.
But are these in the same quantity/concentration and causing as much trouble and being as aggressive as the ones in SF?
There are many people (both in the US and in the world in general) who could quite honestly say the same thing about the homeless in San Francisco... This does not make their situation particularly wonderful, in either case.