Letter of marque and reprisal are terms with very specific meanings. The sort-of declaration of war Congress passed doesn't address either of them.
Reprisal essentially allows an American shipowner who has lost a ship to French (for instance) action to confiscate a French ship in retaliation. The theory is that it all gets sorted out after the war is over.
Not very applicable to today's situation.
From a constitutional dictionary: Reprisal Archaic. An act taken by a nation, short of war, to gain redress for an action taken against that nation. For example, seizing a ship in retaliation for a seized ship.
Not necessarily limited to ship-for-ship retaliation.