100%? Impossible. But they can effectively ban it.

Pass a law that makes any US company, or company doing business in the US, not allowed to host E2EE-enabled apps. This now bans them from the App Store and Play Store. 99% of users won't find or choose to side-load for android users. Then they can make E2EE actually illegal to distribute in the US. They'll almost never bother going after individuals, but this effectively makes hosting a US-based website unable to distribute E2EE programs. So people will need to use foreign sites. Which the US can force ISPs to block via a whack-a-mole on individual sites.

This isn't very likely, but hell Congress was decently close to banning TikTok for no real reason so who knows?