Can the success in rebuilding Japan be duplicated in Iraq?

Absolutely not!
To really understand, you must look at a broader spectrum of things. Japan before the war was a thriving capital of industrial power. The war with China in 1894-1895 made Japan the world's first non-Western modern imperial power, and the war with Russia proved that a Western power could be defeated by a non-Western State. The aftermath of these two wars left Japan the dominant power in the Far East, with a sphere of influence extending over southern Manchuria and Korea. During WW1 it declared war on the Central Powers, attacking German colonial outposts in East Asia, and taking advantage of the opportunity to expand its influence in Asia and its territorial holdings in the Pacific.
The post-war era brought Japan unprecedented prosperity. Japan went to the peace conference at Versailles in 1919 as one of the great military and industrial powers of the world and received official recognition as one of the "Big Five" of the new international order. With that said, it is sufficient to say that then and even in its history, the Japanese have always been a proud people. But as most of you know, within the course of one war (WW2) Japan’s prosperous Imperial Empire was nothing more than a firebombed and radiation drowned, shell of a country. The Japanese Empire's government was dismantled under General Douglas MacArthur and replaced by a constitutional monarchy with the emperor as a figurehead. But it was still, a united Japan. The whole of Japan was united under one religion, unlike Iraq. Japan also had an enormous amount of national pride left, and believed that it once again was destined to such prosperity. With the assistance of American reconstruction (though it was undoubtedly our responsibility, the obvious reasons for the assistance was anti-communist oriented) and the unity of the Japanese people, Japan was quickly rebuilt.
Iraq on the other hand is completely different. A site on constant military conflict, Iraq has never been a world power. Due to the post-Saddam Hussein power shift from Sunni to Shia, Iraq has turned into a ubiquitous region of sectarian violence and anti-American strife. Making reconstruction impossible.