回复：谢谢, 早点问就好了. 受到银行来信说已经报告IRS, 我们需要做什么吗?

I don't see the tax issue here.  I see the custom currency declaring issue.  If your parent declared the $20,000 on form Fin105 when entering the issue, all you need to do is to present the form to IRS if they send you any letter regarding this. Just wait and see, don't volunteer anything at this point.  It is nota big amount, you may not hear anything from them.