Visitors traveling to the U.S. are required to be in possession of passports that are valid for six months beyond the period of their intended stay in the U.S. Citizens of the countries listed below are exempt from the six-month rule and need only have a passport valid for their intended period of stay.
The document then proceeds to list 126 UN members + Taiwan, so 65 countries short from the full list of UN members minus the US itself. Some countries missing from the list include: Albania, Bahrain, Congo, China, Equatorial Guinea, Ghana, Iran, Iraq, Jordan, Kazakhstan, Kuwait, Laos, Morocco, Namibia, Oman, Rwanda, Samoa, Senegal, Sierra Leone, Solomon Islands, Somalia, South Sudan, Syria, Tanzania, Tonga, Turkmenistan, Uganda, Vanuatu, Yemen.
How does the US determine which countries appear on the list?