Paramount on Wednesday began laying off more than 2,000 employees, a long-awaited consequence of its merger with the Hollywood studio Skydance. The cuts, announced internally by David Ellison, Paramount’s chief executive, will initially include roughly 1,000 employees in the United States across many divisions, including CBS News, the Paramount film studio and cable networks like MTV, Nickelodeon and BET. The rest of the cuts, some of which will affect Paramount’s international employees, will come later.