The article doesn't mention selection bias, which almost certainly colored these results. It seems likely to me that externalities other than programming skill biased the entrant pool.
In the US, the best programmers I know have jobs in programming that earn them quite a lot of money. When they go home at night, they may not want to write more code. If they do, they may choose to contribute to open-source projects or their own startup ideas. They're certainly not lining up to enter some silly NSA contest.
If you offered me $1000 to spend my weekend coding some contest, I'd decline. I make enough money programming the other 5 days of the week that I'd rather have my weekend to myself. Or, if I needed some cash, I could make more with those days doing a one-off consulting project.
For a programmer in India or China, that money is worth a lot more (relative to cost of living), and they're not getting paid nearly as much for their full-time job. So, I'd argue that programming contests like this (and TopCoder) have a stronger attraction for non-American programmers and, in order for the results of this to be at all interesting, that variable needs to be controlled for.