Copies made by search engines don't need authorization, and can be unauthorized copies. Search engines are allowed to make copies under Fair Use since they are transformative - see Authors Guild, Inc. v. Google, Inc.

There hasn't been an explicit decision for ML training, but everyone's assuming that Authors Guild v Google applies.

https://en.wikipedia.org/wiki/Authors_Guild,_Inc._v._Google,.....

CDNs operate under the control of the copyright owner, so they would be authorized.

Web browser caches are under the control of the recipient who has authorization to make a copy.