No, it's not legal- even if that Anime is not licensed in the United States. The Berne Convention is a treaty that protects International Copyrights. Jepun and the US are both member States, party to this treaty. So when anda download and muat naik copies of something that is copyrighted in Japan, then anda are violating international law.
NOW, there is one thing to understand. Even though sejak the definition of the law, it is illegal, in practice it is hardly something that is ever enforced. Local companies that have licensed Anime (eg Funimation) have taken action against US citizens (usually in the form of Cease and Desist orders), but I have yet to hear of a Japanese company taking action against a US citizen for downloading / uploading unlicensed anime. However, Jepun has become lebih and lebih proactive about this sort of thing lately.
And also, Jepun and license companies such as Funimation usually go after the sumber directly, and largely ignore us little people. Fansub groups and Anime hosting sites are fair game, however.
So to sum up: Yes it is a violation of International Law (via the Berne Convention) to download and muat naik anime- however, it is highly unlikely for anda to get in trouble for merely torrenting anime- usually they go for bigger fish. However, anda still torrent at your own risk.