Isn't that part of the original building code. The White House didn't originally come with air defense systems.
Considering who Iran's enemies are no use using something from last century. Iraq, Afghanistan, Libya, ect is pretty good incentive not to be defenseless. The US lost it's only chance when they sent Saddam in.
Have to wonder if the US just gave Israel the plans for the bomb in hindsight and there was only a patsy rather than a spy.

If attacking them was such a sure thing it would have been done a decade ago. I notice air-craft strikes are quietly being taken off the table.

Israel already proved they will go after suspected nuclear plants, now there is a real one in plain site they just let it keep working like it should. Not real consistent in their action/reaction pattern. One form of defense would be an EMP let off so far above the plant that it was a few km from affecting ground equipment, that would certainly fuck up anything coming in if the airwaves were flooded right after that with other countermeasures.