CDC posted this today, December 3, 2021
"If you plan to travel internationally, you will need to get a COVID-19 viral test (regardless of vaccination status or citizenship) no more than 1 day before you travel by air into the United States. You must show your negative result to the airline before you board your flight."
SUMMARY
In response to the omicron COVID variant, the Biden Administration today released new guidelines for inbound travelers to the U.S., including U.S. citizens. Effective Monday, December 6, all U.S. citizens, regardless of vaccination status, will need to show proof of a negative COVID test taken within 1 day of travel, or documentation of having recovered from COVID-19 in the past 90 days, before they board their flight to the U.S. The “mask mandate” for interstate transportation and international travel was also extended through March 2022. This comes on the heels of a ban on foreign travelers from eight countries in southern Africa that was put in place last week.
DETAILS Below and at Link
See details published by CDC December 3, 2021: https://www.cdc.gov/coronavirus/2019-ncov/travelers/testing-international-air-travelers.html