Reciprocity

More countries will do this.

Mali and Burkina Faso will impose a travel ban on Americans in response to President Trump’s announcement this month that citizens of the two West African countries would be barred from entering the United States from Jan. 1.

Both governments said in separate statements on Tuesday that they were acting “in accordance with the principle of reciprocity,” and would apply the same restrictions on Americans that were imposed on their countries. The travel bans would take effect immediately, they added, and the decision was announced after Niger made a similar decision last week.

Usually absolute bans aren't at issue, but if you've ever wondered why some country requires difficult-to-obtain visas for Americans, it's because the US requires it of their citizens.