I don't want the russian-style ban enforced by ISPs
Probably punishing companies who pay YouTube for ads would work
And actually I think just banning them from conducting any business, accepting payments/etc, would be mostly sufficient. They could continue to operate at a loss, but it would put American corps at such a disadvantage that domestic social media might be able to compete, and enforcing regulations against domestic companies should be far more feasible.
Man it's nice to live in the country not prioritizing internet censorship