It depends on the nature of the Iranian response:
If they strike at US and Israeli interests via terrorism, well, that's not anything really new is it? Tehran is already doing its best to start a civil war in Iraq and has triggered a war between Lebanon and Israel just last year. So, if this is their plan, it really amounts to more of the same.
However, if they mean that they will fire SSMs at US and Israeli targets (as the article indicates), then that would probably be the last action Iran ever took. No nation, be it the US, Israel, Russia, or the rest of the Gulf, would be able to sit back as missiles rain down around the region (just use your DEFCON training to think about how destabilizing such a situation would be
). Such an act would force the West's hands to strike back at more that just nuclear sites. We would be forced to hit every conceivable missile launching platform imaginable. Iran would have steel raining from the skies on a regular basis.
That still wouldn't require a ground invasion, though. I only see a ground invasion if some of those missiles contained chemical weapons. That would kick things up a notch. In that case, it wouldn't take much to redeploy the 130,000 US troops in Iraq into a irresistible strike force headed towards Tehran (no doubt with Marines landing along the coast and airborne dropping to seize key political targets). In short, it would be over for Iran in such a situation.
I must say that I am somewhat taken aback by the defense of Iranian President Mahmoud Ahmadinejad that some have mounted here. Has everyone forgotten that
1) While speaking to students at a conference entitled “The World Without Zionism” on October 26, 2005, Ahmadinejad called Israel “a disgraceful blot” and quoted Ayatollah Khomeini, the former Supreme Leader of Iran, saying “As the Imam said, Israel must be wiped off the map.”
2) That he said: "Anybody who recognizes Israel will burn in the fire of the Islamic nation’s fury...Any (Islamic leader) who recognizes the Zionist regime means he is acknowledging the surrender and defeat of the Islamic world.”
3) On December 8, 2005, Ahmadinejad gave a speech at a summit for Muslim nations in Saudi Arabia that denied the Holocaust and suggested Israel should be moved to Europe. “Some European countries insist on saying that during World War II, Hitler burned millions of Jews and put them in concentration camps,” said Ahmadinejad. “Any historian, commentator or scientist who doubts that is taken to prison or gets condemned. Although we don’t accept this claim, if we suppose it is true, if the Europeans are honest they should give some of their provinces in Europe — like in Germany, Austria or other countries — to the Zionists and the Zionists can establish their state in Europe. You offer part of Europe and we will support it.”
4) Despite increased condemnation by the international community, including many Arab and Muslim nations, on December 14, 2005 Ahmadinejad again denied the Holocaust took place and called for Israel to be transferred out of the Middle East. During a live nationally televised speech on Iranian television, Ahmadinejad stated:
"They have invented a myth that Jews were massacred and place this above God, religions and the prophets. The West has given more significance to the myth of the genocide of the Jews, even more significant than God, religion, and the prophets, (it) deals very severely with those who deny this myth but does not do anything to those who deny God, religion, and the prophet. If you have burned the Jews, why don’t you give a piece of Europe, the United States, Canada or Alaska to Israel. Our question is, if you have committed this huge crime, why should the innocent nation of Palestine pay for this crime?"
5) That non-muslims living in Iran must now wear colored badges indicating their religious faith, a la Nazi Germany?
I realize that it is fashionable to be a Bush-hater these days, but don't let your political dislike for one leader force you to embrace a rabid anti-semite!