PCR test within "One Day" of arrival in US
According to the news and CDC website https://www.cdc.gov/coronavirus/2019-ncov/travelers/testing-international-air-travelers.html#:~:text=Air passengers traveling to the,all passengers before boarding.
the new guidance as of 12:01am EST (5:01am GMT) on December 6, 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."
Full details are at the link.
That could be problematic if you have a post-tour stay or long layover in someplace like Dubai if flying Emirates.