https://www.eff.org/deeplinks/2023/07/you-can-help-stop-these-bad-internet-bills Another call to oppose the bad internet bills.
Noting that "STOP CSAM" (it seems that this Congressman is borrowing an Australian phrase here to try to spook you) would likely result in a lot of censorship and over-reach for no real gain.
Distribution of actual child porn is already illegal. Sites already have to take this content down.
They're not required to invade your privacy though, and this clause is in existing law for compatibility with the Constitution.
Sites are also not typically held liable for content they don't know / didn't know about.
Think about it for a moment, that would create all kinds of problems for anyone looking to run a website.
It would also likely chill legitimate expression... We know what large platforms can be like. Giving the government the power to censor online content on a whim would do much of the same.