You might also consider that Germany was conquered then completely occupied by US, France, England, and Russia. Iraq was liberated but there is still a guerilla war going on. Germany is not a model for Iraq expectations.
There are desperate guerilla elements that would rather die than see us succeed. That is unsettling, but they will be a thorn in our side for only so long. At some point, the war reconstruction will be done, and a new government and social order will take over. Once people see that their lives are better without Saddam, attitudes will change. It is the aim of the U.S. to make that happen. We will have to enforce good government and responsible spending at the point of the bayonet for some time, much longer than the Adminstration is admitting. We can't have Iraq sliding into a theocracy or another dictatorship, and we need to ensure that their oil money is spent wisely.
In the long term, the game is rigged to succeed. At some point, Iraqis will begin to travel, and ideas will spread. Syrians will wonder why they don't have free speech, Saudis will want accountable government, and a righteous upheavel will take place in the Arab world. Before all that, however, we need to set an example for them to follow. We've built nations before, and despite what any government official tells you, we'll be in Iraq long enough to get the job done.