There is no international organization that I'm aware of. Though maybe you can have your stuff copywritten abroad, maybe you should check out that option. I think in America it's enough to send in a recording.

BTW, if that rapper does steal stuff from others, and is getting away with it, he just hasn't been caught yet. If he's stealing from a U.S. artist, he'll be in trouble sooner or later. This has nothing to do with the country he lives in, but with the country the artist he's stealing from lives in.