I'm not an expert and it would be interesting to hear from someone who has actually tested this but I found a few things and here ae the summaries and links where I found them-

https://www.gov.uk/foreign-travel-advice/usa/entry-requirements
If you are visiting the USA your passport should be valid for the proposed duration of your stay. You don’t need any additional period of validity on your passport beyond this.

https://help.cbp.gov/s/article/Article-905?language=en_US
As a general rule, passports must be valid for six months beyond the date the traveler will exit the United States, however, the U.S. has signed agreements with a number of countries to waive this requirement. When such an agreement is in place, the passport must be valid for the entire period of the visitor's intended stay, but the additional six month validity period is not required.

It’s confusing and convoluted, but it’s found here: https://fam.state.gov/searchapps/vi...ks=D&url=/FAM/09FAM/09FAM040309.html