This comparison probably doesn't make a lot of sense: the US's reconstruction of Japan is backlit by Japan being an industrialized nation with an educated workforce, in a country with basically no domestic conflict in the century prior to WW2. Afghanistan was and is not industrialized to nearly the same degree, has nowhere near the same degree of educational penetration, and has a long history of domestic conflict in the forms of colonialism and sectarian violence.

In other words: $1 in 1945 Japan goes much further in terms of development than $1 in 2000s Afghanistan.