Just to clarify a few things for the original poster:

I think you're probably talking about security (where they search for weapons before you get on the plane) rather than customs (after an international arrival, where they look for things you're not allowed to import or for which there is a duty to be paid).

There are new high-powered x-ray machines used for scanning CHECKED baggage for security (i.e. before your flight). I don't think there's any danger to your CAMERA from these machines, although any FILM you might have in your checked luggage would be likely be ruined. This scanning process happens behind the scenes at most airports. Concerns about loss, theft, damage, and liability limits are completely in order, though; I would NOT put anything very expensive or difficult to replace in checked baggage if I could avoid it.

The x-ray machines used for screening CARRY-ON bags are basically the same that have been used for a number of years. The radiation dose to your baggage from these machines is quite low. You have the right to request a hand inspection of your film at U.S. airports, but you probably won't be able to notice the difference if you run ordinary film (say, ISO 400 or less) through a few times. In any event, there is no danger to your camera there, just your film.

Does this clear anything up for you?