The United States has a treaty relationship with countries who are party to the Convention and the Additional Protocol.
The treaty provides a mechanism for service of documents by a foreign central authority.
Requests are prepared on the Model Convention form (link below).
Despite the title of the Convention, no formal Letter Rogatory is required.
The Convention form serves that purpose.
Here is a link to the model request from for an Inter-American Service:
And here is a link to the Additional Protocol: