From a West German point of view:
The occupation of Germany 1944/45 could of course have failed and foregone a long era of mutual hostility.
But on the whole the Germans were surprised in a positive way
First, the average American soldier was much less resentful than American propaganda would want him to be. A lot of rural bumpkin Whites and of urban Blacks simply enjoyed a state of affairs where they could live more comfortably than at home or where at least they lived more comfortably than their German neighbour and could act as the rich uncle who distributed goodies between the foreign kids (for a whole generation Blacks were identified with distributing sweets).
Moreover, a lot of German-Americans, of Republicans and of Blacks weren’t interested in the war and weren’t (from different reasons) convinced of American moral superiority, even if they deemed warfaring as their duty.
Of course, nearly every American soldier felt that his “democracy” was a better system than the German dictatorship, but (and this is a really important BUT) Americans also felt and communicated that in their kind of democracy you could feel completely welcome and equal even if you were an adherent to conservative, traditionalist, rural, regional, religious or family values. American democracy was insofar a completely different experience from the well-known French democracy (where conservatives, traditionalists, rurals, regionalists, religious people etc. were unwelcome or even “the enemy”). This basically was what gave democracy a new and positive image.
Last not least the most resentful people had left the occupation army rather early: German-speaking Jews, who had played a big part as translators in the first months, were eager to go back into their civil businesses; and after the death of Roosevelt and the retreat of Morgenthau the “Morgenthau boys” lost track and left, too .
So there were a lot of good psychological reasons why the occupation worked well. None of these seem to have been understood by the Neocons, when they tried to imitate the model of the Good War in Iraq or Afghanistan.