If Brin lived in Russia, spoke Russian, and wrote books in Russian we wouldn't call him American just because he wrote a few books in English too.
Perhaps you're not familiar with the history of that part of the world, but the individuals that I named were Persian speakers, who lived in a region that is called the Greater Iran today, and wrote most of their work in Persian. But in all fairness, Arabic was the lingua-franca at the time so they wrote books in Arabic too.
A better example would be to call Grigori Perelman an American mathematician because he published his work on arXiv [1].