Statistically speaking, the average life span is higher in Israel than in the United States, so apparently it is safer to live here.
Hashem decides how long our lives are. No one else can determine that. If someone dies in a terrorist attack, it means that they were meant to die and would have done in the US if they had chosen to live there.
The only exception would be (possibly) if the person chose to live somewhere that was declared a dangerous place by the Gedolim and they said that one is forbidden to go there.
If someone is going to die anyhow, it is way better to die in Eretz Yisrael, al Kiddush Hashem (and receive all the reward that entails) than to die a meaningless death in chutz l’aretz.