According to this blog post on the Washington Post website, The Motion Picture Association of America estimates that online piracy amounts to a net loss of $20.5 billion dollars a year. However, once you narrow in the window onto American pirates, it is figured that the industry only loses around $446 million dollars a year, subsequently less than what they claim.
There is a grey area in which the numerical figures are to be calculated. We cannot say that money is lost from the industry as it is uncertain if a person who illegally downloads a movie would have actually bought it in the first place. In this instance, the entertainment is at the expense of the entire film crew, but not even. On the other hand, there are cases in which thousands upon thousands of works are downloaded immediately after release, quite at the expense of the industry.
While there may be detrimental damage done to the music/film/television industries by online piraters, there is no harmful repercussion done unto our economy. Money not spent on a $20 movie winds up being spent elsewhere.
As SOPA, the Stop Online Piracy Act, has been pulled from Congress' agenda due to severe uproar amongst the citizens of America, the ball is in the entertainment industry's court. My guess is that Congress will create a new Anti-Piracy Act, but one slightly more lax and less threatening of American's first amendment rights.