There's a new executive order for travel, including international travel:
https://www.whitehouse.gov/briefing-room/presidential-actions/2021/01/21/executive-order-promoting-covid-19-safety-in-domestic-and-international-travel/
The interesting part is section (a), part (ii) - following any CDC guideslines to quarantine after entry into the U.S.
Sec. 5. International Travel.
(a) Policy. It is the policy of my Administration that, to the extent feasible, travelers seeking to enter the United States from a foreign country shall be:
(i) required to produce proof of a recent negative COVID-19 test prior to entry; and
(ii) required to comply with other applicable CDC guidelines concerning international travel, including recommended periods of self-quarantine or self-isolation after entry into the United States.
(b) Air Travel.
(i) The Secretary of HHS, including through the Director of CDC, and in coordination with the Secretary of Transportation (including through the Administrator of the FAA) and the Secretary of Homeland Security (including through the Administrator of the TSA), shall, within 14 days of the date of this order, assess the CDC order of January 12, 2021, regarding the requirement of a negative COVID-19 test result for airline passengers traveling into the United States, in light of subsection (a) of this section. Based on such assessment, the Secretary of HHS and the Secretary of Homeland Security shall take any further appropriate regulatory action, to the extent feasible and consistent with CDC guidelines and applicable law. Such assessment and regulatory action shall include consideration of:
(A) the timing and types of COVID-19 tests that should satisfy the negative test requirement, including consideration of additional testing immediately prior to departure;
(B) the proof of test results that travelers should be required to provide;
(C) the feasibility of implementing alternative and sufficiently protective public health measures, such as testing, self-quarantine, and self-isolation on arrival, for travelers entering the United States from countries where COVID-19 tests are inaccessible, particularly where such inaccessibility of tests would affect the ability of United States citizens and lawful permanent residents to return to the United States; and
(D) measures to prevent fraud.
(ii) The Secretary of HHS, in coordination with the Secretary of Transportation (including through the Administrator of the FAA) and the Secretary of Homeland Security (including through the Administrator of the TSA), shall promptly provide to the President, through the COVID-19 Response Coordinator, a plan for how the Secretary and other Federal Government actors could implement the policy stated in subsection (a) of this section with respect to CDC-recommended periods of self-quarantine or self-isolation after a flight to the United States from a foreign country, as he deems appropriate and consistent with applicable law. The plan shall identify agencies’ tools and mechanisms to assist travelers in complying with such policy.