“Major platforms operate with global content moderation rules.”
There are no global content rules.
I think the author meant that platforms formulate their own content rules for the set of global rules in place for countries they want to operate in. These are not technically First Amendment violations since the US Government did not generate the censorship rules. What the US congress should do is pass laws that have severe sanctions against countries that fine US companies for internet content. If these countries want to control content then they need to scan their internet content and do their own censorship..... or else disconnect from the internet. And good luck dealing with Starlink.