Do us Border guards check your laptop and iPhone, etc for pirated movies and music?

Is it really that common? Or do they just run it through the X-ray? What would they do if they saw you had movies on it? I'm a bit nervous

Neither…

US Border guards are looking for dangerous things, not copyright infringement. They don't care whether you have movies and music on your computer. They care whether you are a threat to national security and public safety.

And, if they were to view the contents of your computer and encounter a motion picture file or a music file, they have no way of knowing the history of how it came to be on your computer. For all they know, you have the original disks at home. Of course, if you're a dweeb when you're going through a US Border, they may become annoyed enough at you to try to get you for some piddly thing like copyright infringement.

Not likely. They may just open a laptop to see if it's real ( no hidden compartment for smuggling ).