ここにはしっかりとland ports of entry at U.S.-Canada borders to be fully vaccinatedとあるし、
TRAVEL ALERT: Beginning on January 22, 2022, DHS will require non-U.S. individuals seeking to enter the United States via land ports of entry and ferry terminals at the U.S.-Mexico and U.S.-Canada borders to be fully vaccinated for COVID-19 and provide related proof of vaccination, as COVID-19 cases continue to rise nationwide.
ここにも明白にentering the U.S. by landもfully vaccinatedでないとだめだと書いてあります。
Whether you are entering the U.S. by air, land, or sea:
Foreign nationals must be fully vaccinated against COVID-19 before entering the U.S. Accepted vaccines include FDA-approved or authorized or WHO Emergency Use Listing vaccines.