Actually, Perfect Blue was pretty violent in my opinion. It was also relatively well received by american critics. (they keep describing it disney meets hitchcock though

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If you are talking 'Fist of the north star' exploding bodies type stuff, well I don't think it has as much impact.
Watching people explode who are not very well animated sounds bad but I don't think it compares to more realistic violence. Perfect Blue had a couple drawn out murders and the people looked like people, the bodies had more realistic reactions to pain and that made it more horrific to me.
Some how it makes me cringe because I could almost imagine pain like that..but seeing bodies just twist and explode....I dunno, maybe that's just being desensitized by falling anvils and T.N.T. at work.
....my point being, I don't think too many americans would be upset. Our primary religion uses a device of excecution as it's symbol after all. Now put some gratuitous sex and there and you'll have a picket line in no time
(yeah, I once saw an 18+ sticker on a ranma video in media play)