And why not? Wittner focuses on general backward stupidness: the treaty would “override” the Constitution or the importance of families or the rights of parents. He points out the treaty’s support for parents and families and the impossibility of overriding the Constitution — which we might note in any case says nothing on the subject.
Then Wittner mentions some more substantive reasons for opposition:
“… in fairness to the critics, it must be acknowledged that some current American laws  do clash with the Convention’s child protection features. For example, in the United States, children under the age of 18 can be jailed for life, with no possibility of parole. Also, as Human Rights Watch notes, “exemptions in U.S. child labor laws allow children as young as 12 to be put to work in agriculture for long hours and under dangerous conditions.” Moreover, the treaty prohibits cruel and degrading punishment of children―a possible source of challenge to the one-third of U.S. states  that still allow corporal punishment in their schools.”