the difference between iraq and iran is that saddam hussein was a secular dictator and iran is run by a theocracy. the long term goals in the middle east should be secularization - that is, decolonization, deislamicization. saddam hussein was an asshole, but he was keeping the religious out of power, and he should have been kept in place for that reason, as it was obvious that taking him out would unleash a pandora's box of religious extremism, and that was what we got. then, we had to go in and erase isis from history.
in iran, it's the opposite; the religious extremists are in power and the population is largely fairly moderate. iran is a white country that is relatively european in culture but has been colonized by arabs and islamicists that are trying to enforce their rules on a population that doesn't want it.
regime change can plausibly work in iran; it was obviously going to fail in iraq, at least in the medium term.
now, i need to be careful about this. it has to be done the right way, and iraq is a poor model. i'd actually like to see a united nations mission that is led by the turks and indians on a mission to remove the irgc, because it is an illegitimate and undemocratic terrorist group. that would look more like afghanistan, which was the right way to do iraq, but suffered from the problem that too many countries realized it was a bad idea and wouldn't vote for it.
i would like to see canada vote in favour of a united nations mission to remove the irgc and push for regime change in iran, as we voted in favour of removing the taliban after 9/11.