The United States used diplomacy to broker peace agreements primarily in Israel, Northern Ireland.
In the case of Israel, the U.S. played a crucial role in the peace process between Israel and its neighbors, including the Camp David Accords and other negotiations. In Northern Ireland, the U.S. was involved in the Good Friday Agreement, which helped to bring about peace in the region.
The other options listed do not reflect significant U.S. diplomatic efforts leading to recognized peace agreements in the same way.