Virtually every air traveler entering the U.S. is required to show a passport. More specific information for travelers from many English-speaking countries outside the U.S. can be found at these websites:
New Zealand: www.passports.govt.nz/
United Kingdom: www.gov.uk/government/organisations/hm-passport-office
The U.S. State Department has a Visa Waiver Program (VWP) allowing citizens of many countries to enter the United States without a visa for stays of up to 90 days. For a full list of countries in the VWP, consult the State Department's website. Even though a visa isn't necessary, visitors from VWP countries must register online through the Electronic System for Travel Authorization (ESTA) before boarding a plane or a boat to the U.S. Travelers must pay a fee and complete an electronic application providing basic personal and travel eligibility information.
Citizens of non-VWP countries must have (1) a valid passport that expires at least 6 months later than the scheduled end of their visit to the U.S.; and (2) a tourist visa.
For information about U.S. visas, go to travel.state.gov/content/travel/en/us-visas.html.
Unless you're arriving from an area known to be suffering from an epidemic, inoculations or vaccinations are not required for entry into the United States.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.