有这个说法。美海关边境保护局（CBP)规定：

“Minors may be able to travel to another country without either one of their parents, as long as they have a notarized written consent letter from both parents.........A person under 18 is
defined as a minor or a child”.

“Due to the increasing incidents of child abductions in disputed custody cases and as possible victims of child pornography, Customs and Border Protection (CBP) strongly recommends that unless the child is accompanied by both parents, the adult have a note from the child's other parent (or, in the case of a child traveling with grandparents, uncles or aunts, sisters or brothers, or friends, a note signed by both parents) stating "I acknowledge that my wife/hu*****and/etc. is traveling out of the country with my son/daughter. He/She/They has/have my permission to do so."

CBP also suggests that this note be notarized.

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.

Adults traveling with children should also be aware that, while the U.S. does not require this documentation, many other countries do; failure to produce notarized permission letters and/or birth certificates could result in travelers being refused entry (Canada has very strict requirements in this regard).”

 这就是说，你上面所引的规定（中文）是对的。但从我上面的英文原文规定看，这个规定的执行尺度可大可小。但准备总比不准备要心里踏实得多。