No matter how short or long your trip, make sure you have adequate travel insurance purchased before departure. At a minimum, you need coverage for medical emergencies and treatment including hospital stays and an emergency flight home if necessary. Medical treatment in the USA is of the highest caliber, but the experience could bankrupt you.
You should also consider getting coverage for luggage theft or loss and trip cancellation. If you will be driving, it's essential that you have liability insurance.
Worldwide travel insurance is available at www.lonelyplanet.com/travel-insurance. You can buy, extend and claim online anytime – even if you’re already on the road.