It was quite difficult to find any info (this is the first I’d heard about this). Here’s the github issue where the dev talks about it a bit more and here’s a libreddit with some additional discussion for others like me.

Sharing doesn’t seem to be working. I can still only save or share the link. Not sure if I’m doing something wrong. I closed and reopened the app and the same options persist.

They never said “US”. Other countries have Coast Guards too.