Our catapult system is hardly a secret. The Brazilian and French navies still use the same exact technology with the same parts. The British actually invented the steam catapult system we use today. They used to use it but went to the ramp system to be able to use a smaller catapult, or in some cases no catapult at all. Plus, using Harriers make catapults unnecessary.
Just like the Brazilians and the French, the US still uses the catapult system out of necessity, in order to use some of the larger, heavier and in most cases legacy aircraft. The ski jump ramp is actually less stressful on the airframe of an aircraft since it allows natural physics to do most of the work, rather than the induced physics of the mechanical steam catapult. The new electromagnetic catapults will reduce the airframe stress, require significantly less maintenance, and provide more power for launch. The French and Japanese are aiding in the development of the electromagnetic catapult, so it's not much of a secret, either. It's the same magnet technology that powers magnetic bullet trains.
