What about Israel's isolation amongst its neighbors. If Israel dare strike Iran, There will be bombs, and rockets thrown from the east and the west non stop. If it got worse Iran may send troops to Israel and sacrifice few thousand soldiers who will scare every Israeli. Moreover US involvement wont be popular as they have loads of problems that are only getting bigger back home plus their involvement in two active wars that exhausted US soldiers and US citizens alike. Not to mention Lebanon and the missiles that will be thrown from there. Israel can start a war but it can not stopt it.
Kuwait backs alliances against Islamic State, but no troops (Reuters)
from the article: Iran cleric: Israel wouldn't dare pursue its 'foolish' military threats