Did American submarines resupply at sea?

No, we did not refuel submarines or transfer torpedoes at sea. In order to resupply, our submarines returned to a base. Early in the war, this usually meant Hawaii, Midway Island, or in Australia at Brisbane or Fremantle. As we pushed the Japanese back to the west, we were able to add bases so that submarines would have shorter journeys for resupply.

NOTE: that the German Navy did sometimes transfer supplies at sea and designed specific submarines for that purpose. Most often this was fuel, but it could include food, torpedoes or spare parts.