Do you really believe that there are no US/CA entities simply buying the hosting package in another country to provide this service? I don't have a proof that it's not true, but it just seems really unlikely.

Also - querying (for example) Giganews location I get "Data Foundry, Inc., Austin, TX, US". This really shouldn't be a problem for US lawyers...

Perhaps because their price for customers is strictly greater than zero, their user base is limited?

Hit the nail on the head. For a lot of people USENET is out of their depth. The media companies know about USENET, they have to, but it's not the current popular form of distribution.

Even if bittorrent were to disappear, it seems more likely that sites like Rapidshare would be the next 'mainstream' distribution method.

Besides that, when it comes to bittorrent the end-users have to do some uploading while on the torrent, so the media companies can nail them for distribution. If someone is just downloading content, it's harder to punish them -- from a legal standpoint -- then if you can get them for distributing content.

It hardly matters. If you have to serve a search warrant on a colo facility in Russia in order to get the evidence to take someone to trial then it's irrelevant whether the site operator lives in the US.

As for Giganews, I believe they are protected by safe harbor provisions. For usenet you'd have to go after all of the individual posters, which is something the RIAA/MPAA/BSA doesn't seem to have any interest in currently.