In fact the only cities I’ve been to where I felt like I needed to really have my guard up and head on a swivel were US cities. Not that I don’t keep my awareness up in other places but something about the US sets off my spidey senses. NY felt fine but SF, Miami, Buffalo all felt iffy.
*clarification: I’m not saying that SF is the most dangerous city in the world, but of the cities I have been to around the world, it has felt the least safe.