Where is the mnemonic stored when an account is created in MetaMask Extension? Is it stored in LocalStorage or IndexedDB if it is in the browser area?
If the above is the case, the MetaMask Extension allows you to view the recovery phrase permanently, even though it may disappear in a few weeks due to ITP restrictions.
If it is stored on the server, MetaMask can regenerate the private key with the password using MetaMask/KeyringController and generate the private key to be created in the future, which would be a custodial wallet. Do you have permission to do this in the U.S.?