On January 12, 2021, CDC issued an Order requiring all air passengers arriving to the US from a foreign country to get tested no more than 3 days before their flight departs and to present the negative result or documentation of having recovered from COVID-19 to the airline before boarding the flight. This Order will go into effect at 12:01am EST (5:01am GMT) on January 26, 2021.
It is the responsibility of each traveler to comply with this requirement.
Information on where to obtain local COVID-19 tests including proof of negative results can be found at the US Embassy website of the various countries. A list of these web sites can be found here.