As others mentioned, it has to be done by Americans. A single one would do. Anyone knows when Luigi will be available ?
On a more serious note, dictatorships can not be removed from power by external forces unless it comes with overwhelming firepower (like Iraq in 2003) or the invaders are committed to a long war that will let the targeted nation devastated (Axis nations in WWII). But the biggest problem is what to do after the tyrants are out. As the world learned after Iraq and Afghanistan, creating (or restoring) a culture of democracy, human rights and respect for the laws is no easy task.
It's a theocracy. They basically copied the Vatican model. An ~~assembly of Experts~~Conclave of Cardinals, chosen by The ~~Supreme Leader~~Pope convenes to elect the ~~Supreme Leader~~Pope in absolute secrecy. The thing is, looking back at the last 20 years of American politics, the US is not that different, only it's a Plutocracy. American politicians threw away any pretense of working for, or serving, the people a long time ago.