Actually it is genuine confidence that American is politically incapable of pursuing a military solution. If Iran had any fear in the matter they might actually stop (though it is unlikely). Their pursuit of the means to incinerate millions of their enemies is not the result of any fear, but pure ambition and desire to see human beings cooked, wholesale.
What's truly sad is that these developments are going to lead a lot of conservatives (like myself) to just throw up their hands, shut the doors, bar the windows, and let Europe deal with their coming nuclear holocaust/Islamic caliphate. We sent our young men and women over there to shed their blood for freedom's sak,e and this is what we get?