As a Canadian who moved to the United States this is something that I worry about all the time. That putting myself into this situation might just randomly lead to some random violent event happening to me. I remember that within a month of moving here about a block from me there was reports of someone driving their car down the sidewalk. Just last month someone was high on something, climbed up on the top of the Castro theatre, and started throwing cinder blocks down on people. While that's not really the riskiest situation it kind of summarizes some things that seem "normal" in the US that I would never dream might happen where I am from.