I'm American (born to Indian parents), but I'm not particularly patriotic. In tennis, I almost always root for the Swiss, French, Canadian, and German players. I would root for the Indian players as well, but Somdev Devvarman is almost nowhere to be seen (don't pay too much attention doubles, but will when the Indians go far). I like Fish's game, but the attitude of our American players rub me the wrong way, with players like McEnroe, Roddick, Fish, Serena, and even Harrison being infamous for their on-court behaviors (sadly I was too young for the Sampras and Agassi times, as I loved them).
In other sports, nationalities don't usually matter to me. If I like a particular athlete, I'll root for them regardless of their nationality.