This seems to have been here for a little while, and while I'm not a historian, I do know a little bit about the matter of Japanese nationalism during WW2. Perhaps this article will clear some things up for you.

http://www.wtj.com/articles/gabaldon/

In short, the Japense had been told countless times by their government that the US Military would slaughter them like pigs when we got there, as can be seen by mothers literally throwing their children off of cliffs to save them from the "horrors" the US soldiers would bring upon them; upon the population seeing how wrong that idea was, they were much more willing to let us help them. As seen in these examples.

As for how they got over their anger I presume they had/have after the atomic bombings, a real historian would be better suited to answer that. That first section of that article is a good starting point.

After the war Japan's economy and infrastructure was effectively destroyed and was given the opportunity to restart itself. Due to the circumstances of the Cold War, the United States did not want to lose their military presence in East Asia, so they kept their bases in Japan, and drafted the Japan US Security Treaty to secure a solid position. While this stripped Japan of military power, peace and time for infrastructural spending was just what Japan needed. At the same time, the young Japanese economy had started off stagnant and produced cheap goods. Over time however the economic goal of Japan became oriented heavily towards having a huge global market share. This combined with the protectionist economic policies, which the US gave a blind eye to, in Japan which favored domestic companies to foreign ones allowed Japan to develop their own heavy industries and technology, and by late 70s' and 80s' Japan had surpassed Europe and became the second largest economy in the world. There are many reasons for the huge miracle of the post war Japanese economy, but I think I scratched the surface.