Before entering the United States of America, the one shall think about a visa that will be placed into his/her passport. Under special visa-free regulations, citizens of some countries may visit the country without a permit, however, only if the passport and other official documents meet all requirements.
Moreover, the one shall keep in mind that a visa does not give the guarantee that the one may enter the United States in case if there is no consular officer confirmation from the U.S. Embassy stating that the one is eligible to enter the country.
Only two types of visas are valid on the territory of the United States, those are:
Immigrant Visa which is given to citizens of various countries that enter the country with the intention of the permanent stay in the United States.
Non-Immigrant Visa which is given to citizens of various countries that enter the country with the intention of the temporary stay as tourism, work, business, and studying in the United States.
A Visa Waiver Program allows citizens of the following countries to enter USA without a visa: Andorra, Australia, Austria, Belgium, Brunei, Chile, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Monaco, Netherlands, New Zealand, Norway, Portugal, San Marino, Singapore, Slovakia, Slovenia, South Korea, Spain, Sweden, Switzerland, Taiwan, United Kingdom.
To accumulate a Visa Waiver Program membership, the one shall apply for Electronic System for Authorization (ESTA) 72 hours before the flight. The document is valid for two years after obtaining and allows traveling to the United States.
Among countries, citizens that do not require a visa when entering the USA are Canada, Mexico, Bermuda, Cayman, The Turks, and Caicos Islands.
However, some details shall be discussed as well. For instance, Canadians and Bermudians can stay in the territory of the United States for a maximum of six months.
Citizens of the Marshall Islands, Palau, and the Federated States of Micronesia have a right to enter the country without a visa for business and study purposes in case if s/he may provide a valid passport.
On September 24th, 2017 a president Donald Trump has signed a proclamation that went into effect on December 4th, 2017 and diminished the issuance of visas to citizens of particular countries as Iran, Libya, North Korea, Somalia, Syria, Venezuela, and Yemen.
The visa issuance was restricted on September 13th, 2017 to the nations of the following countries: Cambodia, Eritrea, Guinea, and Sierra Leone due to lack of cooperation with those countries.
An entry ban for nations of several countries as Iran, North Korea, Syria, Sudan, Iraq, Libya, Somalia, Yemen was established as the countries were regarded as the countries with the particular concern on January 27th, 2017, however, expired on 27th of April 2017.