Comcast's broad ownership of NBC and several cable channels and regional sports networks raises antitrust concerns, a cable industry trade group said.
In 2011, the DOJ and Federal Communications Commission put restrictions on Comcast as a condition of its acquisition of NBCUniversal. That seven-year oversight ended earlier this year.
"This is especially troubling because their customers increasingly prefer over-the-top options to traditional video services," the ACA said.
Comcast released a statement saying consumers have more competitive options now.
"We believe that ACA's letter is without merit and constitutes an inappropriate attempt to gain leverage in the commercial marketplace," Comcast said in a statement.
Trump has been a critic of NBC's news coverage and some view his antitrust crusade as a veiled attempt to retaliate against the media companies that he disagrees with.
When the Democratic majority takes over the House of Representatives in January, they plan to investigate whether Trump tried to punish the Washington Post and CNN with "instruments of state power," Rep. Adam Schiff, D-Calif., told Axios. Schiff is expected to be the House intelligence committee chairman next year.
Comcast owns 11 local television stations and is the dominant video programming distributor with 60 percent market share in many markets. Last year, Comcast acquired the NBC station in Boston.