It's not enough to just look at the figures comparitively. While US aid may appear to be huge, proportionally it is stingy - or was. Australia's aid is proportionally higher.
In general, the US has incurred a large debt to the UN, being one of the few members to repeatedly fail to pay UN fees. In general aid, the UN recommends that countries should donate approximately 2% of their funds to aid, however the US donates roughly 0.4%. While 0.4% of US resources towers over 2% of, say, New Zealand's resources, it is proportionally inadequate. That's what my main problem with the US rewaction to the tsunami is.