The biggest country giving the most money isn't very surprising. A fair comparison would be to sum up all the aid from the european countries and the EU and put that in comarison to the USA.
If you want to compare superstates, you don't really get to make your "seven of the top ten countries" thing (though looking at your chart, it's hard to see how the EU would get close to the US from that POV anyway). The better comparison is per-capita typically.