Showtime has given a second season to “United States of Tara.” The premium network has renewed the Toni Collette comedy about a woman with multiple personalities for another round. “Tara” has averaged 2.1 million per week, including repeat airings, which is better than “Dexter” and “Weeds” in their first seasons (the “Tara” number also doesn’t include DVR use or on-demand viewing). Helping matters: Sunday night’s fourth episode climbed 15% over the previous week.