Off the top of my head, I can't think of any anti-monopoly/trust action taken in the US that's been a net positive to the consumer. Can anyone point me to one?

Off the top of my head, I can't think of any anti-monopoly/trust action taken in the US that's been a net positive to the consumer. Can anyone point me to one? Breaking up Ma Bell into baby Bells just created regional monopolies instead a national one. This was largely before my time, though. I've heard anecdotally that consumer prices went up as a result, but I don't know for certain. I was negatively affected by AT&T being forced to divest their cable internet business, leading me to become a long-time Comcast customer through no desire of my own. Now, I'm back with AT&T with fiber to the home. Before AT&T ran fiber (just within the last 2 or 3 years), it was a choice between Comcast/Xfinity or terrible DSL.