Because this is the internet, I have to point out you that you're confusing the Jones Act with the Passeneger Services Act.
The
Jones Act requires that US Flagged vessels are completely US from bow to stern: US built, US owned and over 75% of the crew American. Once that requirement is met, the vessel does not have to comply with the Passeneger Services Act. The
Passeneger Services Act states that
No foreign vessels shall transport passengers between ports or places in the United States, either directly or by way of a foreign port, under a penalty of $300 for each passenger so transported and landed..
Cruise ships have to stop at a foreign port before coming back to the US in order to satisfy both laws, otherwise they can't let anyone get off and stay off. Canada and the Carribean do count, Alaskan cruises that leave out of Seattle stop in BC to skirt both acts. Bahamas cruises out of FLA go to, well, the Bahamas.
Your Seattle/Vancover deal is nice, but in this case, since it is point to point US/Canada it is not covered by either law.