Yeah, you are right
I doubt they'd go after one single person. But if a country had a site like megaupload, then they U.S. might get involved again. But it would have to be really worth it for them to make such a bold move (i.e., more than just one site and probably infringing on the rights of several countries). Really, it's just a bunch of hypotheticals at this point.
All I can do is tell people to back up their stuff, especially for this site. The copyright symbol doesn't guarantee you protection. Even registering your work and getting it officially copyrighted doesn't guarantee you are protected from theft. That's why always keep copies of your drafts from start to finish; that's your proof that you are indeed the original artist.
[link]Well, that's my advice on for people on dA anyway