Pakistan is a nuclear power, but that does not stop the USA from trying to dominate their internal politics.
After that three points to make.
1. After the US puppet Iranian Shah got the ole heave ho, Ayatollah number one let the excellent military the Shah left him fall into rust and ruin. And when Saddam of Iraq saw his opportunity and took it, Iran was militarily defenseless before Iraqi tanks. Iran barely survived the Iraqi invasion and it came at the cost of Iran losing the better part of two generations of men. Nor could Iran buy the weapons to defend itself without US help in the form of Iran Contra.
2. Iran learned its lesson thereafter, never rely on outsiders as they learned to make anti-invasion weapons themselves. As a few of those weapons fell into Hezbollah hands
and were able to destroy State of the arts Israeli tanks when Israel raped Lebanon in 2005. Nor does Iran lack long range ballistic missiles, subs, and other military technology as they have become basically the arsenal of Islam. As I submit Iran has immunity from attack even without any nukes. With all those weapons caches Iran has, a wounded Iran is the greatest threat to mid-east stability. After all, look back into recent history and learn, when GWB&co sold us a phony Iraq war on lies, even the mighty US army and its coalition of the billing, could not control or even slow the Iraqi insurgency from basically controlling Iraq. Iran would be like Iraq except about a billion times harder.
3. Then we come to Israel and realize its totally absurd to think, from a 1000 kilometers away, that they can have a hope of even denting Iran. But Israel can sure force Iran into a war Iran does not want. And then boys and girls, despite what Leon Pin head tells us, and Rumsfeld before Leon, and Les Aspin before than, and we can trace US over optimism back to William MacNamera and even before that. Long odds, with or without US Help, the Persian Gulf will be almost totally shut down for months if not years. The second the first Israel bomb, oil speculators will push world oil prices to over 1,000 dollars a barrel, within a week every oil dependent country will go into a deep depression, and large parts of Israeli cities may become blazing wrecks. The USA did not surrender to the bullshit of the Brits in 1776, why should we assume Iran will surrender to Israeli and US bullshit in 2012?