Personally, I would submit that the ninja tradition - in a more contemporary and thus effective garb - is being continued in a very real sense by the United States Navy’s SEALs.
If you want real Japanese ninjas, just go to the Tokushu Sakusen Gun, Japan's version of Delta Force.
If anybody at all is versed in whatever techniques of the old Ninjas survive to present times, these guys would be.
Anyway, an American with a little bit of training with one of these http://www.albion-swords.com/swords/albion/swords-albion-mark-nextgen.htm would destroy any Ninja, Samurai, or any other Eastern warrior and only may find a decent opponent with European Medieval and Renaissance Knights. I didn't think I would end up going “there” but the silly turn this thread has taken I don't think I am trolling too hard.