Blocking the entire country will do little to hurt the government (who can employ state resources to get whatever information they want) and do quite a bit more to harm the Chinese people by reducing whatever level of information independence they still have.
If there is going to be significant change in China, it will have to come from the Chinese people. Cutting them off from the Internet vindictively does not advance that goal.
There are specific people in China doing specific bad things with specific computing resources. It would be far better for the U.S. government to dedicate more resources to finding and partnering with orgs and projects (like icanhazip or Cloudflare) to find the info they need to apply targeted mitigations.
“China does it, so we should do it too” only makes sense as a strategy if our goal is to become exactly like China is today. I don’t think that should be our goal.