The Marshall Plan only applied to Europe, not to Japan. Following WWII, Europe was devastated with millions of displaced persons, bombed out cities, destroyed infrastructure, poor food supplies and a host of other problems. The Marshall Plan definitely had humanitarian aspects but one of the biggest reasons we did it was to prevent Western Europe from going to communism. There were growing communist movements in several Western European countries due to the chaos. The Marshall Plan helped stem the growth of communism in Europe.

The German government evolved over time. Immediately following the war, Germany was divided into different sectors with each of the major powers controlling a section. Berlin was a special case because while the city was deep in the Soviet sector, the city was divided into Russian, British, French, and American sectors. The civilian government took a while to rebuild because of the official policy of denazification where former Nazis were denied a role in government. The problem was that most of the government officials from before the war were Nazis, so it was hard to find qualified people to run utilities and other government departments. General Patton got into trouble because he realized that there was a shortage of skilled people and so he kept using the former Nazis in many positions. By 1949, we were helping Western Europe rearm as we formed NATO.

The situation in Japan was different. General MacArthur was a form of American Caesar in Japan. He literally wrote their constitution and ran their government for several years. We helped rebuilt Japan over time and helped them evolve from an extremely militaristic government to one of the most peaceful and pacifist nations anywhere. We deliberately provided for almost all of their military defense for decades in the hopes of providing stability in the Pacific. Millions of people (including my late father-in-law) were imprisoned and mistreated by the Japanese during the war. Other countries had to be assured that Japan wouldn't become a military power again. Had we not limited them to their "Self Defense Forces" in their constitution, no doubt many Pacific nations would've gone through an arms race in fear of Japan.

The modern concepts of "nation building" as attempted in Somalia and Haiti were a different situation from what we did with Germany and Japan in WWII. In Germany and Japan, we went into ravaged countries and quickly disbanded and disarmed their militaries. In Somalia and Haiti, we went in with limited means and limited goals into areas where major factions were still armed and willing to fight. We initially went into Somalia in 1992 with the goals of providing food to the starving people. The mission evolved into nation building and arresting Adid. The end result was a bungled military raid that left 17 Army Rangers and hundreds of Somalians dead, followed by an American retreat from the country.