Comcast Corp abandoned its $45 billion offer for Time Warner Cable Inc on Friday after U.S. regulators raised concerns that the deal would give Comcast an unfair advantage in the cable TV and Internet-based services market. The collapse of the deal opens the door for other possible offers for Time Warner Cable, but also casts heightened regulatory risk on merger activity in the U.S. cable industry, which has been rapidly consolidating in the face of competition from satellite TV and Web-based services. The proposed acquisition had faced criticism from some politicians, media company executives and consumer and industry groups, who had worried it would create a monolith with too much control over what Americans do online and watch on TV. Comcast had argued the merger would bring faster service and better video services to more Americans. The Comcast-Time Warner Cable merger would have created a company controlling almost 30 percent of the U.S. pay-TV subscribers, following promised divestitures, and would have provided high-speed Internet access to almost 40 percent of Americans, according to SNL Kagan data.