Sports are like war, some would say it is the modern day outlet for jingoism. There are many parallels between the two, including many expressions and phrases. Athletes are often called warriors, games called battles or war, the national anthem and flag are raised pregame and during medal ceremonies, there are countless examples.
When you choose to represent a country in an international sporting event, that is the country you choose to be identified with. Period.
She chose the country that bombed Pearl harbor and thumbed hey nose at the country that gave her the infrastructure and opportunity to play tennis. If she were raised in Japan or Haiti, she wouldn't be a professional tennis player. She's an ingrate. I hope Americans don't embrace her as American. Much like players who choose to go to ou over Texas or aggy shouldn't be embraced as Texans after using state tax money and resources to learn football.
If she's playing an American, one who reps America, I'm rooting for the American.
Doesn't take away from the fact that she's a great tennis player.