尽量用幽默又软中带硬的话顶回去.比如:

Check the toilet in your house. Probably made in China. What do you think?

如果是在公司年会这种大场合问这种问题,我会咨询HR有什么建议,check the company's Codes of Conduct. 如果HR不得力,问律师这算什么行为.心里有底后可以给他发个礼貌的email. 就直说你feel hurt being asked this kind of question in front of the whole company. Quote the company's Codes of Conduct (such as respect employee's origin, race, etc.). If he is a real man, he will know he was inappropriate and he will be careful next time. If he doesn't care how you feel, then that's not a good environment for you to work. Look for another job.

Don't quote US owes China money.......That's completely irrelevant. That will put the entire company to your opposite side(if your company are mostly local people and you are the only Chinese).