Clearly, if Israel attacks someone there is risk because they are left open to attack from someone else because their military resources are either depleted or preoccupied. If the US steps in and restocks the weapons that have been depleted by attacking, the US clearly has removed a risk associated with the attack. Moral hazard is the notion that those insulated from risk would act differently than they would have if they were subject to the risk. Can you maintain that Israel would behave the same way if their weapons (ie their risk) were restoked (ie they were insulated from risk)?