YouTube's system goes well beyond what is required by the DMCA. Notice no mention of "copyright strike" in the DMCA.
> has adopted and reasonably implemented, and informs subscribers and account holders of the service provider's system or network of, a policy that provides for the *termination* in appropriate circumstances of subscribers and account holders of the service provider's system or network who are *repeat infringers*
https://www.aclu.org/documents/text-digital-millennium-copyr...