Earlier quoted context omitted.
You should never cross any border, US or otherwise, with a mobile phone, laptop, or any sensitive documents. Neither should your employees, if their device are user for work. This is not a new revelation. Industrial espionage by spy services has been ongoing for a very long time.
How would you put this into action if you're a typical business traveler? It doesn't seem very practical.
Prior to leaving on an international trip, the traveler "checks out" a laptop from I.T. for the duration of his trip. No personal or business data should exist on the data at this point. Once destinated, the needed business data can be downloaded to the laptop over a secure VPN back to company HQ.
Prior to returning, the traveler will run a "clean up" script that I.T. has developed. This script will upload any business documents that have been created or obtained while outside of the U.S. back to company servers (over that VPN) and then wipe the data from the laptop. Alternately, the laptop could have a partition set up that, when booted to, starts the reimaging process (sorta like how consumer PCs have a "restore partition"). This would be done, obviously, before returning to the U.S.
When the traveler has arrived back in the U.S., s/he returns the laptop to I.T. who again image it with their gold image and store it for the next user who needs it.
It wouldn't be that difficult or that much of a PITA, IMO -- it all depends on how important the data is to the company. It would likely require a change in policy and some users would almost certainly complain about it. Oh well.