To understand the Arab world’s encounter with democratic modernity—one of the titanic political struggles of our age—it helps to know your Alexis de Tocqueville.

Noah Rothman provides a worthwhile reminder of why a nuclear Iran is a threat not just to Israel, but to the United States:

For one, Iran is the foremost state sponsor of terrorism on earth. It exports terrorists and arms throughout the region and beyond, and there are no guarantees that it won’t play a similarly reckless game with nuclear material. At minimum, the terrorist elements in Iran’s orbit would be emboldened by Iran’s new nuclear might. Their numbers would surely grow, as would their willingness to court risk.

Iran maintains the largest arsenal of ballistic missiles in the region. It can certainly deliver a warhead to targets inside the Middle East, and it’s fast-tracking the development of space-launch vehicles that can threaten the U.S. mainland. Even if Tehran were a rational actor that could be reliably deterred, an acknowledged Iranian bomb would kick-start a race toward nuclear proliferation in the region. The Saudis, the Turks, the Egyptians, and others would probably be compelled to seek their own nuclear deterrents, leading to an infinitely more complex security environment.

In the meantime, Iran would be able to blackmail the West, allowing it occasionally to choke off the trade and energy exports that transit the Persian Gulf and to engage in far more reckless acts of international terrorism.

As for the possible consequences, Rothman observes:

Iranian retaliation might be measured with the understanding that if it’s not properly calibrated, the U.S. and Israel could begin taking out Iranian command-and-control targets next. If the symbols of the regime begin crumbling, the oppressed Iranian people might find the courage to finish the job. If there’s anything the mullahs fear more than the U.S. military, it’s their own citizens.