By default, these kinds of lists are a pissing contest. And that contest is: "Which is/are the most generous nation/nations?"
On it's face you could look at such lists and say "The US is not a generous nation." You would do so because you might say "The US is a wealthy nation, when compared to the rest - it could/should be doing more."
But the wealth of a nation hardly rests solely with what the government can muster. Because the wealth of a nation refelects the wealth of its citizens. Afterall, the government's money is really only the money paid to it by its citizens.
So if you want to measure the generousity of a nation, then looking solely at what its government forks out is looking at only a fraction of the picture. What are the private donations? I'm sure the private donations made on behalf of the US' citizens dwarfs any other country. By miles.
Don't point at stats like "country x = $1.24 per citizen"... because that aint the whole truth here.