According to Gallup, 51% of US adults are very or somewhat worried that they or their family will become a victim of terrorism. It is clear that most of the respondents implicitly understood this to be foreign terrorism, since the principal solutions they supported were changes to immigration visas and bombing. It is wildly irrational to actively worry that you or your family will be a victim of terrorism. There are a thousand more likely ways for them to die, including by other sources of violence. The chances are similar to being struck by lightning. Or dying because of a piece of furniture falls on you.
So the question is why does terrorism get such undue concern? One possible explanation is availability bias. But that’s probably not it. Far more people fear foreign terrorism than domestic mass shooting, for example, and the only difference there is foreign-ness.
I think the best explanation for the evidence is that humans, generally speaking, are hard-wired to fear foreigners. The more different and exotic they are, the more they are feared. We get much more upset when a foreigner kills someone from our tribe than when a snake does, or lightning does, or one of us does. In the modern world, there is no rational basis for that fear.
This truth has lots of consequences for our politics and our policy, which might be interesting to debate, but I’ll leave the OP at this basic premise.