Iran does not have an ICBM that can reach the U.S., and likely will never have one.
Technically, they have one now. They've lofted a small satellite into low earth orbit. Therefore their missile system has the range to reach the US. Granted, it was a very lightweight payload. I've seen estimates on the web that the satellite was on the order of 50 to 60 lbs. A warhead would be significantly heavier, but then, it doesn't have to achieve orbital velocity either.
Iran continues to improve their missiles, extend their capability. A vehicle that can put a heavier satellite into LEO can easily deliver an even heavier warhead on a ballistic trajectory at ICBM ranges... Make no mistake, they want the capability to strike at their perceived enemies - all of them, including us.
I for one would rather not sit here defenseless in the face of a growing threat. We've put a lot of money into missile defense. Seen some successes, and a few misses. I say lets finish what we've started, and deploy the systems.