Here is the official government page on importing pets to the US: Traveling with Pets, Importation of Animals/Animal Products | CDC DGMQ

Actually, it's easier for the cat to get into the US than for most humans! I have heard, however, that some airlines are limiting or even discontinuing the practice of letting pets fly in the passenger cabin. Check around among the various airlines (well in advance) - or see if you can find an animal transport company to advise you about the best airlines and airports. (Your local vet may be able to point you toward an animal transport company.)

I used a San Francisco based service to fly my two cats to Germany from the US - and they did an outstanding job of caring for both the cats, and their anxious owner.
Cheers,
Bev