Suicide bombers intentionally kill civilians--they want that result to happen. Israel knowingly kill the family members of Hamas leaders--they know that it will result from their actions; but they will be happy, not disappointed to find out they weren't in the car after all.
So there is a distinction. But most states treat crimes committed knowingly and those committed intentionally exactly the same. They certainly do so for homicide.
this comment resonates with an Islamic understanding of judgement. The concept of niyat (intention) is a major input to the evaluating the consequences of your actions (in both the material and spiritual regimes). Niyat is of course a major factor in the American judicial system as well - for example, its why some people are charged of manslaughter and others murder-1.
That said, the concept of "collateral damage" is absolutely immoral because it seeks to disavow all responsibility. To take the manslaughter example, consider scenario A, the teenager driving drunk who hits a tree that falls and kills a man. The teen will be charged with manslaughter, because despite the fact that killing the man (or felling the tree) was not his niyat, it was still the direct consequence of his actions. Saying the tree killed the man doesn't work because the "upstream" causal actor was the teen. The tree didn't decide to fall down because teh teen hit the tree, it fell because that was part of the immediate mechanical outcome of the teen's decision to act wrongfully - drive drunk.
Scenario B: If the teen was actually driving sober and lost control of his car because of a road hazard, then there was no wrongful action on the teen's part and the resulting death would not be directly caused by his upstream actions.
Collateral damage essentially argues that the death caused by the upstream is analgous to Scenario B. I disagree, because there is known, finite, and probable outcome that you will it a tree and kill a man when you go out driving sober. However, teh decide to fire a missile into a civilan area, there is indeed a known and probable outcome that noncombatants will be killed. By pursuing the action regardless, you are firmly in Scenario A.
Compare and contrast teh actions of the American military with the IDF - when faced with fedayeen firing from the rooftops of civilian homes, our forces withdrew (and actually lost an Apache). IDF helicopters in the same scenario would have simply leveled the neighborhood.
Collateral damage may be necessary from a tactical standpoint, but it still amounts to manslaughter. Any attempt to justify it is absolutely immoral and indefensible.
UPDATE: Jon H. in the comments points out:
The IDF used a missile strike into a densely populated civilian area in retribution for a Hamas attack against only military targets, which killed 4 IDF soldiers. Killing military personnel doesn't count as 'terrorism'