The CBP told The Register it reserves the right to check "computers, disks, drives, tapes, mobile phones and other communication devices, cameras, music and other media players, and any other electronic or digital devices."
Oh my, you can have fun* with this!
Step 1: Procure as many QIC-80 tapes (or whatever your favorite obsolete tape backup format is) as you can via eBay and the like. Make sure you have enough to catch CBP's attention but still fit easily in your carry-on baggage.
Step 2: Bulk erase said tapes with a very strong magnet. Really scramble that rust.
Step 3: Enter America; when asked "what's on the tapes?" look around nervously and then say "Nothing... Why?"
Step 4: Laugh your ass off as they cart them off to be "inspected" at Uncle Sam's expense.
*Fun levels may vary inversely with melanin levels.