Israel has a lot of advantages against Iran, but it also has 2 major disadvantages. The first is that Iran is huge and Israel is small. The second is that it's incredibly difficult to "win" a modern war. If the Iranian people rally around the flag in wartime instead of "rising up," then Israel is in for a painful war of attrition with a much larger power, and their ability to rope the US into becoming an active participant is nowhere near as great as they think.