According to the Department of Homeland Security, U.S. Customs and Border Protection (CBP) will continue to require non-U.S. citizens entering the United States through land ports of entry and through ship terminals at the Mexico-U.S. and Canada-U.S. borders to be fully vaccinated against COVID-19 and to provide proof of vaccination upon demand.
For travelers outside the United States who are traveling for essential or non-essential reasons, these requirements continue to apply, but they do not apply to citizens, lawful permanent residents, or nationals of the United States.
Non-U.S. travelers entering the United States through land ports of entry or ferry terminals, whether for essential or non-essential reasons are required to verbally attest to their COVID-19 vaccination status and provide, upon request, proof of a CDC-approved COVID-19 vaccination.
Also, they must present a valid Western Hemisphere Travel Initiative (WHTI)-compliant document, such as a valid passport, Trusted Traveler Program card, or Enhanced Tribal Card and be prepared when a U.S. Customs and Border Protection officer requests additional documents.
Keep in mind that the COVID-19 test is not required when entering the United States via an entry port or ferry terminal.