The State Department has allowed US citizens to choose their gender on their own.
Previously, the department requested a medical certificate, birth certificate, or other documents for passport applicants. Now you do not need to provide these documents in order to obtain a gender marker in a US passport.
“ We are working to add a gender marker for non-binary, intersex, and gender non-conforming persons as soon as possible,” reads the department’s website.
Ian Brownlee, Acting Assistant Secretary for Consular Affairs, added that “the processing of adding a gender marker is complex and will take time, but we are committed to getting this right.”
However, at the moment, it is not yet possible to select a gender marker in the questionnaire, since the department will need time to update the system.
Source: travel.state.gov