In North America, the National Association of Theatre Owners (NATO) is the largest exhibition trade organization in the world. According to their figures, the top four chains represent almost half of the theater screens in North America. In Canada, Cineplex Entertainment is the largest and movie theater company with 161 locations and 1,635 screens. The studios once controlled many theaters, but after the appearance of Mr. Smith Goes to Washington, Congress passed the Matthew Neely Anti-Block Booking Act, which eventually broke the link between the studios and the theaters. Now, the top three chains in the U.S. are Regal Entertainment Group, AMC Entertainment Inc and Cinemark Theatres. In 1995, Carmike was the largest chain in the United States- now, the major chains include AMC Entertainment Inc - 5,206 screens in 346 theaters, Cinemark Theatres - 4,457 screens in 334 theaters, Landmark Theatres - 220 screens in 54 theaters, Marcus Theatres - 681 screens in 53 theaters. National Amusements - 409 screens in 32 theaters and Regal Entertainment Group - 7,334 screens in 588 cinemas. In 2015 the United States had a total of 40,547 screens. In Mexico, the major chains are Cinepolis and Cinemex.. How many more theaters does Cinemark have than Marcus Theaters?