This is a response to the standard "I was worried that one time about that Mediterranean-looking dude wearing at a backpack and looking at his watch" anecdote that everybody has, which appeared in a comment which I have screened in order to avoid singling anybody out. You know who you are, but it doesn't matter: at least half the country does it and I'm talking to all y'all.You were "chilled" by a backpacker who was in a hurry?
Look, that's a perfectly normal reaction in America, and everybody who has it rationalizes it as reasonable prudence. The actual recipe is
0 parts reasonable prudence
1 part cowardice
1 part racism
and I recommend you get over it.
It's hard, because human beings can't really emotionally grasp probability. If I tell you "there have been no suicide bombings in the US, and there are 300 million people here, so for any given person there is better than a 99.9999997% chance that acting like they're a suicide bomber means you're a fuckhead", your brain will turn 99.9999997% into "oh, 90% or so" and you will rat the guy out or at least saunter casually off the train. So for the rest of your life, please, for the love of god, live as though you read 99.9999997% as 100% in the sentence above.
(If you're convinced you have to take those small probabilities into account because human life is infinitely precious blah blah blah, please read all of these posts first.)
In Israel there is surely by now a social norm that you don't do X, Y, and Z because people will be rightly worried that you're a suicide bomber and you'll get your shit fucked with. In Israel, then, it may well be reasonable prudence to act against somebody who does X, Y, and Z.
In America, short of actually having a visible bomb strapped to you or screaming "I'm going to blow you all up by pressing this here button in my hand", there are no such lines to cross, because suicide bombing is so incredibly fucking rare it is completely safe to live your life as though it never ever happens. Even our preferred method of mass murder/suicide, the handgun rampage, is statistically completely irrelevant to everyone's actual life.
If you get off the bus because you were scared of some dude with a backpack, you are more likely to get creamed by a passing car than you were to get blown up.
If you get shot or stabbed to death, it will be by a family member, by accident or in a fight. Maybe a stranger in a bar fight or a robbery if you really win the lottery.
If you get blown up, it will be by a gas leak in your house. Maybe, if you really win the lottery, it will be a gas leak in your neighbor's house.
If you change your behavior one iota out of fear of mass murder, you fail.