In some countries the numbers are starting to decline and borders are starting to open up for travel again. However, coronavirus cases in the United States are rising every single day. Some countries have closed down their borders to citizens from the United States. Business Insider has composed a list of the current places U.S. citizens are barred from.
Source: https://www.businessinsider.com/covid-19-where-can-us-tourists-go-countries-block-them-2020-7