Depending on the provisions in your separation agreement or judgment of divorce, you can bring a proceeding against your ex-wife in either Family or Supreme Court. What is unclear from your question is whether the child was returned back to the United States. If the child was brought back, the appropriate remedy is likely to be contempt for violating the judgment of divorce. If the child was not brought back, then you have to consider to what country he/she was taken to, whether that country is a signatory to the Hague Convention and a host of other factors. I strongly urge you to seek a consultation with an experienced family law attorney as soon as possible.
I'm admitted to New York. I had two such cases in 2008 in NYC before the same judge: one absconded to the city and the other from the city. In neither cases did the removal of the child mean anything.
In one case, the stipulation of settlement was as clear as crystal that neither party could leave the jurisdiction, could not alienate the kids from the opponent and even had to foster a relationship with both sets of grandparents. Hence, in that case, simple rules of contract should have yielded results. Instead, nothing. The custodial parent could go anywhere she pleased and the non-custodial had to fork over child support.
In the inbound abduction, during the pendency of a divorce case in another state, the court would not order the abductor parent to return the children to the losing parent. So the divorce proceeded without the abductor parent and the children. Child support was not an issue in that case.
On the other hand, I heard of family court referees ordering the return of New York abducted children under threat of reversal of custody. I do not know by what reason this occurred but I do know the results are mixed.