Here is the full text of the legislation.
https://www.sasse.senate.gov/public/_cache/files/54e9d1de-7b2f-4bba-a6cf-79081e0c9ff0/oll20b20.pdf
This is from the guy, Sasse, who forced PornHub to delete 10 million out of 13 million videos. https://i.imgur.com/3msooBg.png Here, it says that people will be required to verify their age to upload anything, and https://i.imgur.com/AvSYC2p.png here, it clearly states that any computer-generated image (perhaps including 2D digital art), "visual depiction" or "picture" is included under what the legislation covers. If e621 is hosted in the US, I consider this to be a serious threat to its ability to operate as it currently does. Even if not, it's a threat to any US-hosted booru-style site. I suggest that anyone who is similarly concerned about it contacts their congressmen/congresswomen and tells them to oppose it, just as people successfully did with SOPA/PIPA (which they're also trying to do again with different legislation, but that's another topic).
Updated by KiraNoot