I think this is a cultural issue.
American society is laced with frivilous lawsuits; any time an individual can find an opportunity to get rich at another's expense they'll take it. Factor in the millions and millions of dollars a large corporation carries, and you only increase the enticement.
Add to this the increasing absence of parental supervision and instruction and you get the toy laws we have today. The American people also have very set views on cartoons, toys and video games. The overwhelming majority feels these items are specific to children and their offered products should reflect that. Thus, you get GTA3 protestors and the like.
Japan has a far more understanding culture, and the fact that animation is a very mainstream medium helps the cause.