I have never been on a cruise from the US which required clearing customs individually at a port in the western hemisphere. The ships are usually cleared as a whole by customs upon arrival and most countries that cruise ships visit in the western hemisphere have agreements in place only requiring birth certificates and a government id for US citizens arriving and departing via the ship. Re-entering the US does require clearing customs but for closed-loop cruises from the US, the vast majority of cruises from the US, you can do so using a broth certificate and goverment issued id.