The US Department of State issues a level 4 travel warning (categorically no travel. This is the highest level) for the following countries:
Afghanistan.
Belarus.
Burkina Faso
Burma (Myanmar).
Central African Republic.
Chad.
Democratic Republic of the Congo.
Haitian.
Iran
Iraq
לבנון
Libya.
financial.
Niger.
North Korea.
Russia
Somalia.
South Sudan.
Sudan
Syria
Uganda.
Ukraine
Yemen