貌似最好弄一份。
https://help.cbp.gov/app/answers/detail/a_id/268/~/children---child-traveling-with-one-parent-or-someone-who-is-not-a-parent-or
“While
CBP may not ask to see this documentation, if we do ask, and you do not
have it, you may be detained until the circumstances of the child
traveling without both parents can be fully assessed. If there is no
second parent with legal claims to the child (deceased, sole custody,
etc.) any other relevant paperwork, such as a court decision, birth
certificate naming only one parent, death certificate, etc., would be
useful.”