I think it's very tricky statistically to making these type of comparisions between countries because:
(a) The countries must be comparable in size and level of prosperity. Maybe you could make a comparision to China, a country that is nearly four times the size in population to the USA. Now that would be interesting!
(b) You must join both public and private giving not just public. I used to work for a non charitable organisation and it was well known in that sector that the Americans are much more generous than say the Aussies in making donations ala Bill Gates for instance.
(c) You must clearly define the meaning of donations or aid. Donations or aid can be given in many different ways eg food, liberal tariffs, free advice by experts in their field etc etc.
(c) The source and methodology of those making these claims must be clearly stated, honest and accurate. Remember the old adage 'lies, damn lies and statistics!
