Earlier quoted context omitted.
20 years in Europe. I've never never never never tripped over crazy homeless. It's all I do in Berkeley and SF. It's not a small, nuanced difference but literally night and day. Have you really seen tents downtown in any city in Europe? I'm American but most Europeans I know struggle with living in the Bay Area because it's such a shock for them.
SF is also an extreme example of homeless problems because of various factors (weather, systems which attract homeless, etc). There's a homeless problem in other cities, but we don't have tents downtown.
The link below lists around 30 US cities with tent cities downtown.