I think we can all agree the world has become a more dangerous place.
More dangerous than when? before WWII, before the spread of AIDS, before people started smoking tobacco, before the invention of the automobile and related accidents, before the invention of drones or the internet by the US military? Is it really more dangerous or are you just perceiving it that way?
The problem with such generalizations is that it makes it seem like we are all going to die in terrorist attacks when we are more likely to die of a slip and fall in our bathroom or a heart attack. It's like a dog biting a man does not make the news, but a man biting a dog does. People tend to irrationally worry more about the unlikely events than the likely ones.
If you really face an imminent threat every day you would be desensitized to it, not worrying. I've lived somewhere that violent political protests and politically motivated terror attacks were pretty much a daily event for a long time. Where you are in a taxi and your discussion with the driver is what is the best route to get home to avoid passing through a crowd of stone throwing youth or molotov cocktails. I've seen all the cars smashed up in my block during clashes that led to the death of someone around the corner. A bomb went off 3 blocks away one night. I've been a subway train filled with tear gas. That's just a few examples. I could multiply them. If you really are worrying that much about terrorism, then you really have nothing to worry about. Because when it is a real and present threat, you learn to get on with your life and not let fear control you.
Trying to find a needle in a haystack in preventing the one terrorist who is going to come to your suburban neighborhood and set off a bomb is impossible. I'm sorry, but it is impossible. Immigration officers can only do their best but it will never hermetically seal you off in a bubble. Forget about it. The best way to prevent such violence is to deal with the political issues behind such violence. Yes, I said political, because the fact that the violence is from people of one religion perpetrated on another is only a distraction from the political injustices that people feel the need to remedy. People like OBL may couch it in religious terms, but ultimately that's not the reason behind it.