Is there a state that faces a specific existential threat right now? Yes again. That state is South Korea.
South Korea has no nuclear weapons of its own, though the U.S. has extended its "nuclear umbrella." Its immediate neighbor, North Korea, does have nukes, which it tested and developed while the U.S. was distracted in Iraq. North Korea’s leaders are peculiar, to put it mildly, and have repeatedly promised / threatened to destroy South Korea in a "sea of fire" in rhetoric as blood-curdling as any anti-Israel rant from Iran. South Korea's population center is practically on the border with the North, rather than several time zones away as with Iran relative to Israel.
It would be better for everyone except North Korea if it had no nukes, but the South Korean president was not invited to address Congress during the GW Bush years to demand tougher action against North Korea.
Is Israel's situation comparable to that on the Korean peninsula—or, to use the more familiar parallel, to that of European Jews menaced by Hitler in 1938? It most emphatically is not, if you pay any attention to the underlying facts.
The most obvious difference is that Israel is the incumbent (if unacknowledged) nuclear power in the region, with the universally understood ability to annihilate any attacker in a retaliatory raid. The only similarity between this power balance and the predicament of European Jewry in 1938 is the anti-Semitism. In 1938 the Jews of Germany, Poland, France, and Russia were a stateless minority with no military force of their own to protect them and no foreign power (including the U.S.) willing to step in. In 2015 Israel is a powerful independent state, more heavily armed than any adversary.
Think of this parallel: The full-tilt U.S. slave economy of the 1850s and the police-shooting abuses of 2015 have in common racist anti-black prejudice, but they are not the same situations. One was resolved only by cataclysmic war. The other is very serious but not the prelude to north-versus-south combat. The Iranian rhetoric of 2015 and the Nazi death machine of the Reich have in common anti-Semitic hate-mongering. But the differences between them are far more obvious than the similarities.
And is the Iran of 2015 like the Germany of 1938? Oh, please. In 1938, Germany had the strongest military in the world, and the second-largest economy (behind only the United States). Its economy was bigger than France's and England's combined. Today's Iran, by contrast, doesn't even have the strongest military in its region, and its economy is not in the world's top 25. Hitler's Germany was an expansionist force that would grow until it was crushed. Iran makes enormous trouble for the U.S. and others, but no one serious can be proposing that it must be crushed.
I lay this out not imagining that it might change a single word in Netanyahu’s upcoming speech, nor the fervor of those who support him (and will soon tell me so). And of course Israel will decide for itself whether it feels "existentially" threatened. I am writing to an American audience that must assess our next steps and long-term goals toward Iran. When we call this situation "existential," we’re either saying something that is true for everyone—in the age of nuclear weapons all of humanity is at risk—or we’re making a specific observation that is far less applicable in Israel than in many other places, starting with South Korea. It's a slogan that has replaced thought.