It is, but the US and the EU legally recognize each other's copyrights. So he can sue the Chinese company in his country, and when they don't show up send Apple a notice to freeze assets related to the company, which just needs a US lawyer. In the end the lawyers win, but it is a straight forward case (assuming all the facts are as given...)
Yes, you likely could threaten Apple with a lawyer.
But based on your comment you likely have never dealt with a lawsuit, especially involving several jurisdictions. And trust me, the lawyer want the same thing as the scammer. Your money!
Maybe it is better to sue Apple instead, for allowing such apps - they claim they have "strict guidelines" and review all apps before accepting them .... If many developers around the world start doing this, it becomes a PR issue and costs them money too in legal fees ... may even force them to fix the issue.