I was actually having a similar discussion with a friend today and we touched upon the topic of BTC getting outlawed by governments. Hypothetically, what's to

I was actually having a similar discussion with a friend today and we touched upon the topic of BTC getting outlawed by governments. Hypothetically, what's to stop countries and ISPs blocking it on the protocol level, the way China blocks certain types of traffic? Wouldn't that kill it for mainstream use and make it work only on darknets like TOR?