I fail to see how this is racist. Your logic appears to be any joke an American (assuming he is white) makes about any other race (or nation that is primarily of another race) is automatically rascist. His joke was not insulting nor did it portray any negative or otherwise stereotype. Your main problem is that he doesn't know the difference between a Chinese and Japanese name. Oh the horror. You should have a look at your own prejudices. Part of the problem with ongoing prejudice is people get sick of hearing about it because of overly sensitive responses like the one you just made.