Your laptop and a whole lot more can be seized at customs coming into the country even if you are a US citizen, according to the Washington Post:
The policies cover "any device capable of storing information in digital or analog form," including hard drives, flash drives, cell phones, iPods, pagers, beepers, and video and audio tapes. They also cover "all papers and other written documentation," including books, pamphlets and "written materials commonly referred to as 'pocket trash' or 'pocket litter.' "