To put it another way, 9/11 was one big bang followed by a whole lot of payback on our part. In Israel, by contrast, they are suffering a psychological death by a thousand paper cuts, and have taken it for years.
I agree with all you've said and I would only add that they are also surrounded on every side by numerous enemies who would love to see them wiped off the face of the earth. And also the world political community has come down much harder on Israel than on us.