the reason i would support an attempt at regime change in iran is that i know that the vast majority of iranians are not religious, and there is a simple reason for it: they're white. the iranian regime has to be imposed by vicious force because it's extremely unpopular with the vast majority of white iranians. conversely, islam is more popular with the invading arabs, who have colonized the region in the west of the country.
the reason assad is still running syria is because it's a secular society that doesn't want islamic rule. the same is true in turkey, but turkey's politics are confused by ethnic divisions that inflate the muslim minority's power. the lebanese are majority christians. eastern europe knows the history of islamic imperialism, which actually kidnapped their children and brainwashed them into slaughtering their own people. likewise, there have been periodic anti-arab uprisings throughout north africa for over a thousand years.
there are counter-examples, but they are almost entirely constrained to the arab core, of which iraq is in. afghanistan was a secular society before the russian invasion, but something rotten happened there in the intervening years. that might be the whole list.
so, don't be confused. islam is a conservative, controlling ideology and it is incredibly unpopular in most of the world because it is incredibly oppressive. iraq was an exception due it's geography, and not the rule.