Do you think I have a good chance of getting into Harvard College?

You should make sure you have some match schools in the UK and the US, I don’t know what you plan on studying bu the Oxbridge and Imp college options are just as much of a reach as the Ivy option in the USA. I assume you are in a private school on Cayman so take note of where your peers go and what your counselor suggests. How do you define yourself ethnically? Are you black Caymanian? Do you have dual citizenship outside of Cayman?