Nobody can suggest that they possibly thought the Americans weren't contingency planning (which all armed forces do and is a pretty regular thing!).

They would target the nuclear sites....no news there then!

They would also target some military sites....well what kind of news is that?! It's pretty regular practice when targetting specific sites to also attack any military sites that might be capable of blowing your planes out of the sky! And if the trigger was Iranian involvement in US casualties in Iraq this would be perfectly legitimate under international law.

Reasons why the U.S. cannot attack Iran:

Let's not forget that U.S. intelligence on Iran seems to be even poorer that it was on Iraq, and that Iran has hardened and buried many nuclear facilities in a way that would make them difficult to destroy. The threat of Iran being capable (most war-gaming instructions point to this as an absolute certainty) of responding to an attack in a way that obliged the US to escalate the conflict to full-blown regime change is also very real. Lastly (and most importantly), there would be a host of unintended consequences inside and outside Iran.

(actual number is larger, but classified)

An invasion of Iran is highly unlikely - the geography doesn't work, much more populous than Iraq, limited indigenous opposition to the regime, etc.  But a strike against nuclear targets certainly is.  The whole balance of the Middle East changes if Iran gets the bomb.