I am sure those affected need help but what makes you think others can provide help better/faster then Japan itself can?
Perhaps the US navy has lifting capacity that Japan could use, but what else?
http://www.wolframalpha.com/input/?i=population+of+japan
127 million according to Wikipedia.
We have 2.5x the population but 25x the landmass. That's an order of magnitude difference in population density. Now imagine a natural disaster.
I am sure those affected need help but what makes you think others can provide help better/faster then Japan itself can?
Perhaps the US navy has lifting capacity that Japan could use, but what else?