(CNN)Iran is a repressive and anti-American regime that has spread its influence in the Middle East, often to America's detriment. But it is also an ancient civilization, with centuries of power and influence in the region. The notion that the United States could solve all of its problems with Tehran by toppling the regime is fanciful. It has withstood US pressure and sanctions for nearly four decades. And even if it were somehow possible to topple it, look around. The lesson of the past two decades in the Middle East is surely that regime change leads to chaos, war, refugee flows, sectarian strife and more. It opens a Pandora's box in a land already rife with woes.