Over the past 10 years, America has fought in wars in Afghanistan, Iraq, Libya, and across the Arabian Peninsula. The last thing it needs today is another war in the Muslim world.
The first reason is that Iran, despite media reports, is not about to acquire a nuclear weapon. As the IAEA report indicated, there has been no diversion of fissile material from known facilities inside Iran, and without fissile material that the Iranians could enrich to the levels required for a nuclear weapon, they cannot go nuclear. Iran would need either to throw out the inspectors and divert their existing stocks or else develop very large enrichment facilities without their being detected by the outside world. Throwing out the inspectors would be easily observable, and it is unlikely that Iran has covert facilities sufficient to make it a nuclear weapons state any time soon.
Additionally, bombing Iran would merely delay, not stop, its nuclear program. It would also harden Iranians' belief that they need a bomb to protect themselves from the United States and Israel. The different lessons taught by Iraq and Libya on the one hand, and North Korea on the other, would become even starker. The massive bombing campaign that would be required to hit the important sites in Iran also risks rallying the Iranian population behind a regime that has been bleeding legitimacy for years. Iran's likely response could turn the entire Middle East—including Israel, Iraq, and Afghanistan—into a burbling cauldron of violence.
Eight years ago, the foreign-policy establishment of both the Democratic and Republican parties led the American people into a war in Iraq that has had devastating consequences for America and for the world. Many of those same elites are currently issuing calls for another war in the Middle East. Most people who bought lemons from one car dealership go elsewhere to buy their next ones. Given the much greater stakes involved in making war compared to buying a car, Americans ought to think long and hard about buying another war from the same people who brought us Iraq.