As of May 12, 2023, noncitizen nonimmigrant visitors to the U.S. arriving by air or arriving by land or sea no longer need to show proof of being fully vaccinated against COVID-19.
Visitors are also no longer required to show proof of a negative COVID-19 test, effective June 12, 2022.
However, it is best to remember that the travel situation post Covid-19 is constantly evolving. Make sure to refer to the United States’ Centers for Disease Control and Prevention (CDC) webpage for the latest updates on the post Covid-19 travel situation.
Singapore’s Ministry of Foreign Affairs website also provides a comprehensive guide in relation to travelling to the USA.