Travel Warning System.
A travel warning system is provided by the U.S. Department of State, to rate every country and warn citizens of unsafe travel destinations. The system lists every single country, and breaks it down into 4 categories, or travel advisory levels:
Exercise normal precautions
Exercise increased caution (yellow)
Do not travel The criteria for these 4 levels
are based on the anticipated concerns of crime, civil unrest, health, natural disaster, terrorism, or a time-limited event. For a list of all countries: https://travel.state.gov/content/dam/NEWTravelAssets/pdfs/Travel%20Advisory%20Country%20List%20Alphabetical%201-10-18%20VERT.PDF
("Know Before You Go, Breaking down State Departmentís new travel warning system," Peter Greenberg, CBS News
, January 15, 2018)