There were many issues surrounding the response to Katrinahttp://en.wikipedia.org/wiki/Criticism_of_government_response_to_Hurricane_Katrina
(read the whole
I tend to think it's much simpler to offer aid to another country in time of crisis than it is to coordinate it on home soil. You're dealing with local and state government too, not just federal....and all the jurisdictions and red tape that come with that. Its far simpler to get on the phone and offer aid to another country immediately after the event, or release a message to the press indicating it. Then it would be a call to the military to gather the aid up and send it to Japan. Manpower aid can be handled separately without the governments intervention, which was not the case for Katrina.
The real test is how the Japanese responds to this compared to how we did.