U.S. antitrust enforcers will take another shot this week at convincing a court that AT&T Inc.’s acquisition of Time Warner Inc. is bad for consumers. This time they’re bringing real-world examples.

Six months after AT&T completed the $85 billion deal, many of the ills the government warned about when it sued to stop the takeover have come to pass: higher prices, a programming blackout and reduced choice for consumers. By some accounts, the largest U.S. pay-TV provider has played the...