Because foreign ships generally can't engage in commerce between US ports. If they re-flagged to register as American ships, then they'd have to use American crews. And they can't afford to operate without low cost third and fourth world crew.
They can probably buy a waiver from the Biden crime family.
I was on an Alaskan cruise a few years ago. It struck me that virtually everyone who worked on the cruise, when I inquired, was from some eastern European country, or the Philippines,or or Latin America.
I think the ship I was on was flagged in Greece, if I recall correctly.
I remember hearing that Alaskan cruises always make a stop in Canada, but I didn’t know the reason for that.
Not enough. To be American flagged the ship has to have been manufactured in the US, to protect American shipyards. I don't believe there are any American shipyards making cruise ships, and if there were that would have no impact on existing ships. The solution would be to amend the Passenger Vessel Services Act, which imo would be common sense. Simply eliminating the requirement that a ship embarking from the US visit one foreign port would solve the Alaska problem. Even if just for a couple years. And would require Congressional action. The Big Guy can't do it with an EO. He is in office to enforce American law after all. Not that that matters. I give you the cancelation of construction of the wall, Congressionaly approved and funded. Stopping it a violation of the impoundment act. An impeachable act imo. But so what, who cares about laws.