Complex sentence: Many historians view the second wave feminist era in America as ending in the early 1980s with the intra-feminism disputes of the Feminist Sex Wars over issues such as sexuality and pornography, which ushered in the era of third-wave feminism in the early 1990s.
Split into simpler sentences: Many historians view the second wave feminist era in America as ending in the early 1980s with the Feminist Sex Wars, a split within the movement over issues such as sexuality and pornography. These disputes ushered in the era of third-wave feminism in the early 1990s.