We found Noonsite to be good place to start our research. It is comprehensive and you will find an answer.
Unfortunately, while it might be "best available", the information on Noonsite can be quite out of date, and is very infrequently updated. For example, they have the check-in requirements for Puerto Rico quite wrong. Not disastrously so, but obviously several years behind the real world and not in accordance with current regulations. Just look at the dates for the posted comments. There is very little website traffic on Noonsite these days. Official vetted and edited updates of the detailed pages come very infrequently. The PR clearance information was last updated in 2014, despite well publicized changes to small boat clearance procedures in the meantime. In my opinion, Noonsite is "coasting" on name and reputation, and is getting less useful by the year.
Unfortunately, there is no source I have found to have an update cycle fast enough to recommend as really uniformly authoritative. Even the e-book cruising guides that claim to have annual updates we have found to be years behind changes on the ground.
We always check as many sources as possible for information, usually, but not always, finding the website for the national government involved to be the most useful with current requirements, if not always the clearest explanations! Who does the US Customs and Border Patrol get to write the text on their website? I think they farm it out to the same people who wrote the manual for that last electronic gadget I bought from China...
I see so much information posted on web forums and such that is just plain wrong, or at least presenting a highly exceptional case as a generality, that postings of unknown provenance I tend to deeply discount.
We have found SailClear to be a good idea, that isn't actually used by the local officials. Are there any countries that people have found it to actually be used as advertised?
La Perguera, Puerto Rico