Spending two minutes to look on Wikipedia shows that, for example, comparing UK to USA: the UK is technically worse in "homeless per capita" (where homeless includes people forced to sleep in the houses of friends or family) - at 56.1 per 100k for UK, and 19.5 per 100k for USA. However when it comes to "unsheltered", i.e. what people generally think of "homeless" as meaning, and what's visible on streets, the US is far worse at 12 per 100k compared to UK's 0.9 per 100k. (France at 4.5 per 100k, Germany doesn't have a comparable number listed and I'm too lazy to look for one.)

I have lived in two of the European cities you mentioned, visited many others as well as a number of major US cities, and I agree that in all of them it is possible to see extremely depressing scenes with far too many people forces to live on the streets. But it's ridiculous to think you could compare any two city's homeless/unsheltered problems based on visiting or even living in those cities without actually studying the situation / looking at statistics.

Perhaps you read parent comment as implying there are literally zero homeless people in Europe, which obviously isn't true, and technically US and European unsheltered numbers are indeed "comparable" as I've just proven by comparing them - but I feel if the difference is the US having 12x as many people in that position it's misleading, to the point of being effectively wrong, to call that a comparable situation.