Iran has a stew of ethnicities, and some are highly loyal to the Ayatollah. However, as in Iraq rather than Afghanistan, there is at least a strong minority of well-educated citizens.
As Seth notes, it would be enormously difficult to undertake now in Iran what we did in Iraq. However, this is not a task that will get easier if we wait to do it. We have already waited past the "easy" point, and we are close to the tipping point at which a tyranny becomes not only dangerous to its own subjects but also a threat to others. A nuclear Iran with missiles that reach Israel and Europe fits the bill. In that case, postponing attack simply means increasing their advantage and decreasing ours.
By removing the missile defense from Poland and the Czech Republic, Obama has signalled to Iran and its friend Russia his lack of concern with future developments.
Of course, as Barbara notes, Obama is tackling the really important things--going to Copenhagen. Although if no differences divide us, why should he champion Chicago above Rio?