Do you think the best idea is to start meddling in the affairs of a nuclear state with totalitarian government? It's a rhetorical question, but really man... Iran would end up being another Iraq, but with the added jeopardy of nuclear weapon gift-baskets ending up in US/Western friendly countries' laps.
I wouldn't say the current attitude is to ignore the problem, but I would say it's keeping hands-off and wary.
GW Bush was hardly silent on the matter originally, but once he got clued in that they may have a viable weapon... he backed off.
Politically, look at what happened the last time a sitting US president decided to do something about Iran. Bush wasn't grotesquely stupid, and neither is Obama: they won't risk doing something that would cause a bigger problem. Clinton might have had an opportunity to do something about it, but he was a little busy dealing with eastern Europe/Soviet Satellites. Everyone shares blame in not watching the shop, now you just have to make sure no one is still stealing.
At this point, democratic change in Iran is going to have to come from within... I don't like the idea of invasion and the US trying to continue a 3 pronged war. I have a lot of

for the US military's projection of power ability, but this is something that even Red China would have difficulties with.