The above image is a scan of a piece of Trinitite. This is desert sand that was underneath the explosion of the world's first Atomic bomb in New Mexico as part of project TRINITY, hence the name Trinitite. The heat from that blast melted the sand into a green glass, not unlike the Fulgurites that result when lightning hits sandy soil.
Now, imagine an entire nation looking like the above sample, melted into green glass. Buried in the green glass are the charred remains of the people of that nation. It's not an idle fantasy. The US spent $5 trillion dollars (back in the 1950s, when a trillion dollars was REALLY a lot of money!) building a nuclear capability that can actually do that; melt any nation and it's people into a giant slab of green glass. The USSR knew it, the world knows it, Saddam knew it. The government of Iran knows it.
Even if Iraq had possessed weapons of mass destruction (which we now know they did not), and even if Iraq had the long range ICBMs to reach across the Atlantic with (which we know they did not), Iraq would still not have been a threat to the US because any attack with a weapon of mass destruction would be national suicide.
The same applies to Iran. Even if they were pursuing a nuclear weapon (which nobody can prove they are) and even if Iran had long range missiles to strike at America (which they definitely do not) Iran is not going to carry out an unprovoked attack on the United States with a nuclear weapon because any attack with a weapon of mass destruction would be national suicide.