QuoteRight now, U.S. citizens entering or exiting the country with a valid U.S. passport aren't required to let border authorities snap their pic. CBP states:

Travelers who do not wish to participate in this facial comparison process may notify a CBP Officer or an airline, airport or cruise line representative in order to seek an alternative means of verifying their identities and documents. CBP discards all photos of U.S. Citizens within 12 hours of identity verification.

https://reason.com/2019/12/03/all-u-s-travelers-abroad-should-submit-to-facial-recognition-scans-says-homeland-security/#