Source on American charitable contributions:
"Americans gave, per capita, three and a half times as much to causes and charities as the French, seven times as much as the Germans, and 14 times as much as the Italians. Similarly, in 1998, Americans were 15 percent more likely to volunteer their time than the Dutch, 21 percent more likely than the Swiss, and 32 percent more likely than the Germans." [1]<p>So yes, the data is heavily skewed if it does not include private donations, although the OP does indicate that the graph was just a rough draft. But it's also important to note that America has a vested interest in ensuring Haiti's stability, whereas most of the other countries aren't as nearly invested in the country's future. We don't want a Somalia in the Western hemisphere (they're actually not that far from each other from a PPP standpoint - Haiti is ranked 203 vs Somalia's 225 [2])<p>The potential effect of this could be observable through the 2004 Tsunami, wherein many of the listed countries were much more geopolitically connected to the affected countries than the US. If these countries made sizably larger donations, I would think it's because of this factor.<p>1: <a href="http://www.american.com/archive/2008/march-april-magazine-contents/a-nation-of-givers" rel="nofollow">http://www.american.com/archive/2008/march-april-magazine-co...</a>
2: <a href="https://www.cia.gov/library/publications/the-world-factbook/rankorder/2004rank.html" rel="nofollow">https://www.cia.gov/library/publications/the-world-factbook/...</a>