Two common cases cited by proponents of “nation-building” are the great successes that Western powers had in post-World War II Germany and Japan. Even if efforts failed in other places it’s clear that these two countries bounced back from the war to become leading nations in the world, and with the right inputs we can reproduce that kind of success elsewhere, they argue.
(I’ll leave aside the fact that I think this is almost never really a goal for people who make these arguments. Geopolitical and military-industrial concerns are usually paramount, in my opinion, but let’s grant that their intentions are not malicious for the sake of argument.)
The mistake here is that these nations were not “built” after World War II, they were rebuilt. Both were already complex societies with private property rights, industry, law, art, and customs that made them successful. Granted, there were ugly, primitive trends in both societies that were exploited by their governing regimes, but the difference between both societies pre- and post-war was that these regimes were removed. Most of the rest of the epiphenomena of their cultures remained intact, and almost all of what had to be rebuilt was simply physical infrastructure.
In Marshall Plan aid Germany received 63% and 44% of what France and the United Kingdom received, respectively, yet its recovery (after the punitive measures imposed by the occupying powers were lifted) was swift. To this day it is the economic powerhouse of Europe. Japan likewise continued its swift upward trend after the war, stagnating only later due to domestic policies.
In contrast, a country like Afghanistan can mostly only be “built” from scratch. After almost 11 years of American occupation it lacks most of the characteristics that the two major Axis powers had before World War II. I don’t mean to say that economic progress is impossible for the people there, only that any analogies to Japan and Germany are bound to be wrong. On top of that, an occupying military regime hardly has the knowledge or incentives to help a society develop. A country’s own government with all of its powers, offices, and personnel cannot do this, much less a hostile occupying force in another country.