Actually, I think in theory the UN is the right authority to coordinate the response to the recent natural disaster in South-East Asia, but practically speaking this presumes the UN is functioning reasonably close to how it is suppose to be functioning. It is not. And given how corrupt the UN has become -- it is now a coalition of banana republics, terrorist states, and tinpot dictatorships -- the reality is that the US has to take charge.
This way, the developed world knows: 1) the aid will get to where it is suppose to be going, and 2) the money doesn't end up lining the pockets of some corrupt official in a country that changes government through revolution more often that the French go on vacation. So while the UN should be coordinating the effort in theory, realpolitik necessitates the US taking the lead.
That being said, Canada continues to prove its inneptitude by charging a surviving victim $100 to replace her passport so that she can go home, while our Prime Minister continues to enjoy his holiday, and Liberal legislators complain they don't have the time or energy to get personally involved but then they slam America's response. Get me a green card quickly.
The correct authority would be the Church, not the civil sphere.