Holiday, Tourism and Medical Treatment
In general, holiday makers traveling to the U.S. require valid B-2 visas. That is unless they are eligible to travel visa free under the Visa Waiver Program, or they are a national of a country which has an agreement with the U.S. allowing their citizens to travel to the U.S. without B-2 visas.
If you are not eligible to travel visa free, or are not a national of a country where B-2 visa requirements are waived, you will be required to apply for a visa before traveling.
If you need to travel for medical treatment, you should be prepared to present a letter from the hospital or clinic in the U.S. indicating the nature of the illness, the approximate cost and time required for treatment, the date of appointment, and proof of your ability to pay for the treatment. A full list of information required for medical treatment can be found here.