Shares of AT&T traded 1.8 per cent lower after the company said it agreed to Time Warner in a deal worth US$85.4 billion.
Shares of Time Warner last traded 2.5 per cent lower at US$87.27, compared with AT&T's US$107.50 a share's offer.
Investors "expect bad things to happen in Washington," Roger Entner, an analyst with Recon Analytics, told Bloomberg. "Investors are sceptical of the deal being consummated."
Shares of Restaurant Brands International dropped after the owner of Burger King and Tim Hortons posted disappointing quarterly results, underpinning signs of weakness in the fast-food industry.
Burger King's same-store sales rose 1.7 per cent in the quarter, while Tim Hortons' comparable sales increased 2 per cent, the company said in a statement. Both were short of analysts' expectations and a slowdown from the year-earlier quarter.
Shares of Restaurant Brands International traded 4.2 per cent lower as of 1.18pm in New York.
In Europe, the Stoxx 600 Index ended the day at 344.26, a little lower from the previous close. The UK's FTSE 100 Index fell 0.5 per cent. France's CAC 40 Index gained 0.4 per cent, while Germany's DAX Index rose 0.5 per cent.
Syngenta shares slid on concern that China National Chemical Corp's US$43 billion takeover of the Swiss company risks regulatory delays in the European Union, Bloomberg reported.
ChemChina didn't submit so-called remedies in the EU's early-stage review of the deal by the October 21 deadline, leaving the bloc until October 28 to decide whether to approve the deal without any strings attached or open an extended "phase two" probe that could add at least another four months to a decision, according to Bloomberg.
Syngenta shares closed 5.8 per cent lower in Zurich.