Sure the Jones act is protecting "only" 60,000 American jobs. And everyone would benefit a little from cheaper shipping. That's the exact same argument neoliberals made when textiles and furniture and everything else beat a path to Asia and left behind rusting factories and opiod-popping towns. I mean, sure, lots of devastation in the rust belt and New England but hey, we all get cheaper underwear!
The problem is that 60,000 jobs here 60,000 jobs there starts to add up across industries until you get stagnant wages, collapsing labor participation rates, collapsing labor share of income, fraying social net, the worst economic inequality in the history of this country, an ever growing group of hopeless, despondent (or angry) people, eventually, even, Donald J Trump as President of the United States.
A vivid example is Hawaii. Hawaii produces excellent cattle and livestock - plenty of sun and great weather. It is cheaper to fly cattle to the U.S. than it is to transport it in a Jones Act trade ship. There is a weekly Boeing 747 from HNL to LAX to transport cows to the mainland U.S. market. Imagine how much more competitive the Hawaiian livestock industry could be if sea shipping rates were competitive.
As Americans, it is our choice if we want to stimulate and connect our territories to our vast mainland market or if we want to protect special interests, lobbying, and corruption that supports the Jones Act trade.
If Jones Act shippers were fleecing PR, then it would be very profitable for foreign shippers to set up a route from Florida to PR via the Bahamas. This would be 100% legal under the Jones Act and the fact that they haven't demonstrates that it isn't very profitable to try to undercut the current shippers.
The same for Hawaii, all foreign ships have to do is stop in Ensenada and then they can go to San Diego or Longbeach and it'd be 100% legal under the Jones Act. Foreign-flagged cruise ships are already doing exactly this.
Also live animals nearly always travel long distances by air. Putting them on a boat for a long sea voyage means you have to make provisions to feed and care for them, which eliminates any potential cost savings.
Only about a third of the trade comes from foreign ships. Most of the inbound cargo to PR comes directly from U.S. (and mostly U.S. products) thus requiring Jones Act ships. PR is also net exporter (about 50% value add to imported goods) and its largest market is the U.S. (again thus requiring Jones Act ships). So foreign imports/exports are NOT the crux of the issue here.