How to integrate the CMP into Google Sites
Please note: Due to it's closed policies, it is not possible for us to support the automatic blocking code for Google Sites. Even though you can still integrate the semi-automatic blocking code via Tag Manager or injecting the CMP code snippet (consentmanager Account => CMPs => Get Code) directly in the body tag.
https://support.google.com/sites/answer/2500646?hl=en
