Plenty of athletes born in America (unlike Osaka who was born in Japan) compete for other countries that give them dual citizenship, whether or not they know the language. If Japan wanted other tennis players to compete, they could have chosen them, same with all the other countries who choose players, often Americans, to compete who did not grow up in or live in their country. Check out the Israeli baseball team, for instance. Which is fine.
The rest of your criticism isn’t even worth responding to.