There is no point registering a cruise ship in the US, because the Jones Act says that to operate on internal US routes, ships not only have to be US-flagged and crewed by majority US citizens, but also have to be built in the US.
This is mostly to protect the US merchant marine and shipbuilding industry for reasons of national security.
The thing is, there are no yards in the US that build ocean-going cruise ships. So the companies ensure that every cruise has at least one stop outside the US, making it an international voyage on which they can use foreign-registered ships. The terms of your ticket say that if you leave the ship before you reach the foreign port, you’re on the hook for the company’s fine for the Jones Act violation.
