I can: Our outrageous amount of wealth.
This goes hand-in-hand with income inequality, of course, but given the vast amount of capital in the country, we should be way higher. Ok, Singapore, Finland, Taiwan, etc., maybe unreachable because of the huge difference in geography and culture, but we should AT LEAST be up there with Germany and Britain- two other large, Western countries.
I don't buy the "ethnic diversity" angle, either. Canada is about 22% nonwhite to 30% for the US and they're not just ahead of us, they're ahead of most of Europe as well.