Alex, I am not sure there were any US ships.
At the bottom of this link:
https://www.britisharmedforces.org/p...ed_lockyer.htm
it says: "There is a memorial plaque on the esplanade at St Nazaire, close to the French War Memorial and a plaque in Saint-Michel which lists all the ships which helped in the rescue. (of the Lancastria)- Baharistan, City of Lancaster, Clan Ferguson, Dundrum Castle, Floristan, HMS. Havelock, HMS. Puniari, HMS. HIghlander, HMS. Vanoc, Ulster Prince, Cambridgeshire, Cymbula, Fabian, Glenaffaric, Oransay, Robert L. Holt."
I don't think any of the those ships are US ships.