You think China could make the US government make a private citizen censor the Internet in a different country?
1. Stopping trade with America would completely destroy China. They could bluff, but they have very little actual leverage. Their economy is hugely dependent on the US.
2. The US government is not really a fan the Great Firewall or of the Chinese government. It's unlikely it'd just be cowed into submission, especially with Trump in office.
3. Even if the government wanted to not upset China, I don't see how it could stop Starlink legally. You think a law would pass that would make it criminal to distribute uncensored information in China? There would be so much public outrage at that. I can't imagine either party supporting it at all. Plus, I can easily imagine that being struck down as unconstitutional. It would spend forever in the courts at the least.
4. Even if it did pass, Starlink would just move to Canada or South Africa or somewhere before it services China. In no scenario can Musk lose his billions. The US loses half its space economy, but there's no mechanism to take his money or to actually stop Starlink.