Importing Pets to the USA
From VjWiki - The Immigration Wiki
To import your pet in to the USA you will have to deal with 2 sets of requirements.
- The requirements of the airline you are flying with
- The state laws in relation to animal importation
Airlines all vary on their specific requirements. It is strongly advised that you check the airlines requirements before you book your flight.
You can find the Animal Import Regulations for all states at the USDA APHIS Veterinary Services
There is no quarantine for cats entering the United States, nor are there entry requirements for rabies vaccinations, microchips, or health certificates. Cats are subject to examination at the port of entry to rule out any zoonotic diseases (diseases that can be transmitted to humans) and may require veterinary medical examination, treatment, and/or quarantine if they appear ill.
Although cats are not subject to rabies vaccination regulations, once they have entered the country all pet cats are also subject to state and local vaccination requirements.
Some airlines will only let you put your cat in the hold during the flight. For the cat, in-cabin is way better. Less noisy, better temperature, and you're there to reassure the animal. If you are bringing the animal in-cabin it's recommended that you use a 'Sherpa carrier', as it's possible to get them in a size that will safely fit under the seat in front of you.
For old cats, the Cat Guru (Mags) advice is: take them to the vets first of all and get them checked over. Tell the vet you are considering flying.