United States of Al entered CBS' successful sitcom arena to middling ratings. Its 0.58 out of a weaker Young Sheldon 0.69 is passable. But again, B-Positive would have likely registered a similar rating had it been positioned in its 8:30 timeslot. For now, it debuts as On The Bubble as more performances are needed to measure the trajectory.
Elsewhere, B-Positive moved to the 9:30 timeslot behind a weakened Mom's 0.55 rating and registered a 0.42, losing 0.17 of blood. This performance was similar to Sophomore Unicorn's performance when Mom registered similar numbers. B-Positive's swift downgrade is ode to CBS handed its freshman sitcom a test of strength and the sitcom did not demonstrate to built an audience. CBS wisely decided to revert back to only allowing its "show builder" timeslot to to used for a partial season.
Back when The Big Bang Theory was the mammoth and the 8:30 timeslot was open, several shows only enjoyed partial exposure and were expected to demonstrate growth. This came at the start of the 2014-15 season when The Millers squandered the lush lead-in, and five episodes in CBS axed the freshman series and handed it over to neglected sophomore Mom. The power-up was brief, and CBS only allowed Mom enough time to gain an audience before affording the same opportunity to The Odd Couple, and Mom passed the grade demonstrating it had an audience.
Another season CBS used this strategy was 2016-17 when Joel McHale marqueed The Great Indoors. The show underperformed so low it barely met half of The Big Bang Theory's extreme ratings, so low that lead-out Mom beat it on several weeks. CBS tested the sitcom's strength and farmed it to Monday, where it tanked (and repeats of TBBT outperformed it). CBS recognized the series was not sustainable and cut their losses. The network opted away from this strategy when Young Sheldon debuted to shiny numbers and the network opted to keep it planted to build an audience, forecasting TBBT would soon end.
Imagine if CBS would have implemented this strategy last season and tested The Unicorn at 9:30 vs burning off freshman series Broke in the back. The Unicorn could have likely flown, and Broke may have been given more exposure to grow. Mom is on its way out, and CBS likely tested B-Positive to see if it could potentially sustain the 9:00 hour in its exit. That is unlikely now, leaving the future of sitcoms in this hour in question.
