The US enjoys overwhelming military superiority against Iran. In a conventional conflict, the US would be able to handily win with cruise missiles, fighter planes, and big guns from ships at sea. The US spends about 80 times as much per year on defense as Iran and its dramatically larger economy allows it to withstand the costs of war far better. Iran’s gross domestic product is only about $357 billion, roughly a 40th of America’s GDP of $14.66 trillion.
This is not to say Iran can’t cause trouble if it comes to blows. In addition to missile systems that can reach US allies like Bahrain, and one or two that might reach as far as Israel, Iran has cultivated close ties to two key military groups on Israel’s borders: Hezbollah in Lebanon and Hamas in the Gaza Strip. It’s possible it might convince either group to step up attacks on Israel if it came to war, doing damage to that country.
But the US response to any effort to shut the Strait of Hormuz, which would cause the price of oil to skyrocket, would be punishing and swift, knocking out most of Iran’s ground defenses and much of its controversial nuclear program for good measure.