There are some sources on the Internet but I would take them with a grain of salt because I have no idea how reliable they are…
This article has 20+ sources listed at the bottom, some of which (at a glance) seem to be very relevant to what you’re looking for - Spanish Observers and the American Revolution, 1775-1783, Spain and the Independence of the United States, Spain, Forgotten Ally of the American Revolution.
This page also has a list of sources. Does anyone else know of anything that might be helpful?
endowdly replied to your post: Hello, I really love your blog. I’m 15 y/o and I’m mexican. I love history, and I am passionate about it. I’m doing some research of the Spanish influence on the American Revolution. There’s very little information about the topic. Do you have information that could be useful? I’d be really grateful if you could help me.
Maybe check the Georgia and South Carolina State Archives? I believe the Spanish in Florida had a little influence there. Just a guess.