> Turn off the internet (like Iran).

Unworkable without societal collapse happening shortly thereafter. Iran is politically stable through massive authoritarianism and oppression, not due to limitations on the internet (it's not turned off).

> We can (see China); we chose not to.

It's a catch-22. We could technically if our population supported massive reductions of freedom and freedom of speech, but to gain that support we'd need to do the latter first to get to a highly powerful widely supported government. It also hinges very, very much on having and trusting a generally benevolent government. All in all, a terrible option in your simplistic form.