In 1994, Nielsen auditioned for a role in "French Kiss". While director Lawrence Kasdan felt she was inappropriate for what he wanted, he encouraged her to try her luck in America. After moving to the USA, she finally achieved a breakthrough when she was cast in a pivotal role in "The Devil's Advocate" (1997). As Satan's sensuous daughter, Nielsen cut a memorable figure as a seductress who plies her trade on Keanu Reeves' somewhat innocent lawyer. Similarly, her one scene in "Permanent Midnight" (1998) saw her as a sexy German woman who in the throes of passion with a drug addicted screenwriter (Ben Stiller) utters a disturbing but amusing line. Even in the superior "Rushmore" (also 1998), Nielsen was cast primarily for her looks, playing the fantasy-inducing mother of a prep school student.
Nielsen hitched her ascendant star to the femme lead in the "Soldier" (1998), portraying the mother of a mute son whose lives are altered by the arrival of Kurt Russell's titular character. Although the finished product didn't exactly live up to her expectations, the actress emerged with respect and a newfound status as an action film performer. Brian De Palma tapped her to play the sole female member of a "Mission to Mars" and Ridley Scott cast her as Lucilla, the conflicted sister of a despotic emperor (Joaquin Phoenix) in "Gladiator" (both 2000). While the former barely utilized her except as a plot device, the latter epic offered her a meaty role. With her regal bearing and stunning looks, Nielsen perfectly captured the languid hauteur of the privileged but proved enough of an actress that she could convey layers of emotion with a single look. (For example, her scenes with Russell Crowe's fallen general turned gladiator crackle with barely suppressed erotic energy.) Her performance made it clear that Hollywood had barely begun to tap into her capabilities.
In 2002, Nielsen co-starred with Robin Williams in the feature "One Hour Photo". In this thriller, Nielsen portrays a woman who is stalked by an employee (Robin Williams) of a one-hour photo lab. The following year, she was cast in the action crime feature "The Hunted," which co-starred Oscar recipients Tommy Lee Jones and Benicio Del Toro. Neilsen also made for a quintessential film noir femme fatale in director Harold Ramis' pitch black "The Ice Harvest" (2005) as a strip club owner who considers an escape with a mob accountant (John Cusack) after he steals a bundle from his boss.