Todio,
Dinosaur saved me a lot of time and money with the heads up on the U.S. Customs Certificate of Registration. You only need the carnet if you are going to more than one country for extended periods of time. It is a declaration of your gear and what your intentions are. It is also a a type of insurance policy. It is also VERY EXPENSIVE. I went to our local customs and got the skinny on the Cert. of Registration. It was all I needed to get through Toronto and Tel-Aviv customs.
Good Luck!