Is there a way that this email can be disassociated from my Apple ID?

An Apple ID is simply an email address with anybody who provides email accounts. You don't really provide any information about the email account itself. If you are referring to an iCloud Mail account, that is part of the Apple ID. It cannot be changed or removed but you can use an alias instead. Add and manage email aliases for iCloud Mail on iCloud.com - Apple Support

If it is with another provider, then it is already disassociated and I am completely failing to understand the problem here.

The other possibility is that instead of changing your email address used for an ID, you created a whole new account. You need to change the address on the old account, not make a new account. Unfortunately the email address you just used for the new account cannot be used again so you will need yet another email address for your new identifier on the old account. The support article Change your Apple ID - Apple Support outlines various methods for changing the email address (Apple ID) you use for your Apple Account while retaining everything in your account.