Obviously, Square eventually started tweaking things again for Final Fantasy, but the foundation had been laid. The first truly successful Japanese RPG gave American audiences an idea of what to expect from the genre, and studios all around the world would follow in those footsteps. It proved that they didnt need to adjust the difficulty or dumb down the plot just tell an epic story and let us get lost in it. 25 years later, Final Fantasy VI still sets the standard.
Source: N4G PC How Final Fantasy VI Made Role-Playing a Hot Property in America