If Puerto Rico were independent it could start doing deals with China which the US doesn’t want, I read a whole book about that once which I can’t remember the details of super well but maybe the book would interest you.
America’s Last Fortress: Puerto Rico’s sovereignty, China’s Caribbean Belt and Road, and America’s National Security
By Alexander Odishelidze
No problem. The author is definitely a lib who wrote it from a pro-US perspective as a warning basically, like “if you don’t stop treating Puerto Rico like shit they’re going to leave you for China” but if you can look past the ideology I think it’s got some good info.