system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is the U.S. the closest ally of Japan even after WWII?

Is the relationship as perfect as it's made out to be? Any other facts you can throw in there?
gpt
Imperial Japan died at the end of World War II.

The US then embarked on a nation building campaign that has never really been equaled.  We *rebuilt* Japan from the ground up.  Their economy, their society, their technology, everything. 

Then we forbade them from having a large military (they only have a Self Defense Force)... and promised them that the US military would defend them if they were attacked.