The US informally agreed not to use Privateers, if Spain did not.It'd probably be easily doable in the Span Am War. Something intended to allow more raiding of Spanish supply ships to their Colonies at no cost to the USN. Also maybe for longer ranged raiding hitting some spanish flagged merchant ships off the Canariez and in European waters also at no cost to USN. Perhaps with the goal of forcing the Spanish to devote more warships to Home waters and less available to send to the Caribbean. Also if the US German war scares over Samoa and Venezuela had gone hot I could see privateers being used
They also did not sign the anti-privateering agreements
So while both countries had privateers available, neither issued Letters of Marque
The Navy did buy a number of Civilian Ships and commissioned them into the USN as naval auxilleries, who typically had kept their civilian crews, while having a USN Captain and XO to assist with the Blockade of Cuba, and a number of Spanish vessels were captured that way, and crews did receive Prize Money even.
Other were used to drag and cut Spanish Communication cables.