The question I would ponder on, would be what exactly were the safeguards that the Bush Administration took before entering Iraq to ensure this scenario would never arise in the first place. (the Taliban gaining the upper hand in Iraq)

If the majority of the population are Shia, just as in any other democracy then, one would expect the majority to rule. If they are a majority of democratically elected Shias, with a bias towards America, well, what have we actually gained?

One cannot legislate to enforce a change of mindset, I'm afraid, and I don't believe Iraq (or any other, mainly Muslim country) can ever effectually do that.
One can legislate for equal rights; employment, pro choice in all matters relating to the person, etc. But if the democratically elected majority do not pass such laws, where does a democracy then become a dictatorship.

And what rights do 'We' have, to go back in there, and sort it out, again?