It depends if the divorce was legally performed.
If the divorce was performed legally in accordance with the local state laws and requirements, in the state of USA where it was filed (or where it will be filed) and both spouses have been duly served before, during and after the divorce process, the divorce will be valid in Dominican Republic.
The parties still need to record the divorce before either the closest Dominican Republic Consulate (if both parties are now living outside the Dominican Republic) and/or before the local authorities in the Dominican Republic, if one of them still lives in DR.
By doing that parties will be able to officially update their civil status (from married to divorced) before all corresponding authorities in the State where they got divorced as well as in the Dominican Republic.
Not recording the divorce decree in DR does not means that they are still married in Dominican Republic, just that they legal status has not been updated and that could create inconveniences in future.
Now, if the divorce was not legally performed under the laws of the US State where it was obtained and the spouse residing in Dominican republic at the time of the divorce was not duly and legally served before, during and after the divorce, then the parties might still be legally married in the Dominican Republic as well as in the State where one of them filed/got for divorce, notwithstanding said party might have a divorce decree in his/her hands issued by the US court.