Well I've personally never met a ninja, but I'm sure theres one somewhere. I dont think that they were too violent, as a kid I was exposed to all those 'American Ninja' movies starring Michael Dudakoff, they were ultimate cheesy! The ran in the middle to late 80's. I guess that because America is this one big melting pot, we are exposed to almost every culture, so far off ideas like ninjas are no big woop over here.
The marketing guys probably figured that "ninja" would not sound good in the ears of parents looking for toys for their little children, ninjas being cold-blooded assasins and murderers. Maybe americans are more ok with murder and death as entertainment for children, but I think the main reason for the name difference is that the toys were introduced in europe a while after the US release. Maybe there had even been some controvercy over the name in USA before the Europe release. *shrug* Anyway, I remember being quite annoyed about the whole "hero turtles" thing when I was a kid. "Ninja" sure did sound a lot cooler to me.
best non-Star Wars flick = Evil Dead 2: Dead by Dawn
It's simply hilarious! If you love characters like Jar Jar or if you just like slapstick in general or if you like a good scare at night, Bruce Campbell (star of the movie, plays Ash) and Sam Raimi (director) have you covered.
P.S.: Sam's little brother, Ted, plays the Possessed Henrietta.