I recently committed to the college of my choice, do I have to rescind my other pending offers of acceptance or can I just let them be?
Let them be. You don’t have to do anything.
You don’t have to “rescind”. But it is polite to let them know you won’t be attending. (You never know if you might want to transfer in the future – best to leave on a good note). You can see if there is a way to turn them down in their portal, or if there isn’t, send an email to the main admissions email address.
Agree with the above. While it is not required, it would reflect well on you personally as well as you HS if you let the other schools know you won’t be attending. Some make it easy to do (portal, postcard) or else you can send a brief email to admissions.
It is polite to let colleges know you won’t be attending. They usually give you an option on the portal, or a postcard to send back. If they don’t, you can just send a short email to your regional rep asking that your application be withdrawn, as you won’t be attending.