"Is the ski jump supposed to take the place of the cats?"
Yep.
The USNS is the only service to have figured out how to make a cat work right.
If you have ever been below decks to see them, you can understand why.
Rube Goldberg would have been proud.
Well Uncle Sam has been nice enough to sell it to the French navy as well!!!
I think it was a British Navy idea...
They were invented by the Brits, IIRC, and used by several Navies, although usually on ex Brit or ex US ships. One exception would the be the French, who started (or restarted) after WW-II with ex US ships but went on to build their own. The current one, "Charles de Gaul", is, like it's namesake, something of a disaster.