Hi Jennifer, Sarah from WorldNomads.com here.
If your policy does not already include cover for the USA, you will need to purchase a new policy. If it does include cover for the USA, you should be able to extend it. So we can advise you further, please use the contact us page on the World Nomads website so we can look at your policy and let you know how to proceed.
Safe Travels. over 8 years ago