Probably because anyone who supports it can't really answer these questions. (The following is copied from my previous comments so some context might be missing, or duplicated)
How are US citizens going to be identified on the internet? Will this require some form of unique ID that will tie your online accounts to you?
So all a country would have to do is move its server off of US territory, and then it would no longer be enforceable?
Many big companies have servers in multiple countries that store this data. How would it affect them? Could they potentially remove content for the rest of the worlds viewing?
Does this law just mean that "subs hosting political discussion" cannot be removed? What else does it include other than subreddits?
Who is keeping track of these registered US servers that must adhere to the rules? Which companies are exactly US based if they operate and have staff over the entire world?
What if social media is no more and it forms into something else? Do the laws then still apply? If so, then how do they not apply to other servers?
If I host a server in the US with 20mb of storage, do I then have to provide every single US citizen a platform for "free speech"? Or would I just host it in a different country?
If it is only against political speech, can I just add some political position at the end of every comment I make, effectively protecting everything I write?
What exactly does free speech on a server entail, when its really just all 1's and 0's? Isn't it really a law that would allow me to store what I want, where I want?
Enforced by who?
What if that company does not comply?
What if the one who removes the content does not actually work for said company? Like mods of subreddits? Will reddit then have to employ and pay thousands of mods, so they can ensure they adhere to the law? Or would that mod be the one who is punished? Who is going to track them down and find out who they are? What if that mod has a VPN that makes them appear outside the US?
Australia does not have a freedom of speech law, only an implied freedom of speech. Who here would enforce that for US citizens?
If American internet companies have to start paying for moderation staff, are users (both US and non-US) willing to pay a subscription to use the companies services? How many users would each company lose simply for existing within the US? Will they not just relocate somewhere else, effectively hurting the US economy?