At the very least, the two WW2 cases started with a multi-year military campaign where the enemy's cities were bombed to rubble before a single U.S. soldier occupied those nations. That approach seems to be conspicuously absent from all of the nation-building crap we've seen since then.
Another thing that is conspicuously missing is a formal declaration of war against an enemy nation, too.
Let me fill you in on a little secret: When the president of the United States stands up and declares that the nation is engaged something as silly and banal as a "war on terror," you know damn well that the @sshole doesn't intend to actually win anything.
Also, Germany was a European or Western country that was already somewhat familiar with democracy-the ill-fated Wiemar Republic. While Japan we spared the Emperor who got on board with us. With regard to Iraq, after taking out Saddam’s regime, we should have just put in the local version of Mubarak and not have been quick to disband the original Iraqi Army.