Paul Graham's incorrect argument assumes that all countries will produce great programmers in equal proportions to their populations. He couldn't be more spectacularly wrong.
People from other countries where tribalism (Pakistan), extreme deference to authority (China), and extreme elder worship (India) are the rule, fall to the ingenuity, independence, creativity, and innovation of Americans, every, single, time. The majority of the cultural and genetic makeup of the continent for its first 500 years was that of people willing to risk their lives to come here, work hard, be independent, and make their own way. The effects of that are not easily undone. Paul Graham has fallen into the fallacy of thinking that all countries are the same, all cultures the same, all people the same, and thus their outputs should all be the same. What a dolt!
My company has an Indian subsidiary that we use to handle some of our simpler engineering issues at lower cost. And that's the point. They handle the simple issues, because even their best engineers can't be trusted with our complicated issues. We have to solve those ourselves.
So while the US may only have 5% of the world's population, it's not inconceivable that we could be producing 95% or better of the great programmers already.