What the US requires of its citizens is something that the U.S. Department of State might stipulate. What is being alluded to is that neither the ICAO nor the UN require certain information as a matter of treaty. Therefore the US Department of State cannot say that all information they say is mandatory is required because of the ICAO. AFAIK, the ICAO governs the nature of passports, e-passports or the like for travel by public airliner. AFAIK the U.S. Department of State does not.