NEW YORK — Comcast is dropping its $45 billion bid for Time Warner Cable after heavy regulatory pushback.

A combination of the No. 1 and No. 2 U.S. cable companies would have put nearly 30 percent of TV and about 55 percent of broadband subscribers under one roof, giving the resulting behemoth unprecedented power over what Americans watch and download.

Competitors, consumer groups, and politicians have criticized the deal, saying it would lead to higher prices and less choice.

“The proposed merger would have posed an unacceptable risk to competition and innovation, including to the ability of online video providers to reach and serve consumers,” Federal Communications Commission Chairman Tom Wheeler said in a written statement.

One of the concerns consumer advocates and competitors had with the Comcast deal was that it could undermine the streaming video industry that is reshaping TV. Comcast could, for example, require onerous payments from new online-only video providers for connecting to its network. Dish, the satellite TV company behind the new Web video service Sling TV, and Netflix opposed the deal.

“We always structured this deal in a way that would enable us to walk away,” Comcast chairman and CEO Brian Roberts said in an interview on CNBC.

“We have to live with it, and respect that, and move on,” Roberts said of the government’s opposition to the deal.

With the deal between Comcast Corp. and Time Warner Cable Inc. called off, a transaction with Charter Communications Inc. aimed at smoothing the way for regulatory approval also falls apart.

Even with the Comcast and Time Warner Cable deal being nixed, cable companies are likely to keep combining as costs rise for the shows, sports and movies they pipe to subscribers and video customers decrease.

Many analysts expect that Charter Communications could resurrect its own effort to acquire Time Warner Cable.