Anyway, they interviewed a number of foreign born founders, and the consensus was that it took so much risk to move to another country as an immigrant, the risk of founding a startup really seemed small in comparison.
Having grown up in Central America in the 80's myself, I'd also postulate that you're able to think outside the box a bit better as well. Why? Because to the immigrant, everything in a new country is so profoundly different to begin with, that you barely see the boxes that so many other native-born people are hung up on.
But there is a big difference between applications and their usage in certain international markets. Even if web applications are international, many apps are mainly focused on a North American/ Western European market.
Sure, you have to fly and find somewhere to stay, but you have to do that from most places in the US too.
In fact, non-US founders seem to do better on average than US founders. I'm not sure exactly why; probably because they have to be more committed, and commitment is the biggest predictor of success in a startup. But whatever the reason, YC clearly works internationally.
I think software/web startups are basically international now. It's all one big market. Now all we need to do is explain this to the governments.