Yes, you can use Betfair in the USA.\n\n Therefore, US residents that live outside the particular state, would need to use a VPN, like Atlas VPN, to change their IP to the New Jerseyan one.
The beauty of the idea was that people could now also bet against something happening - and set their own odds. Betfair makes its money by taking a commission ranging from 2-5% from the winning customers after each event.