I would think dual citizenship would normally come through a parent via birth and the constitution of the parents’ countries’ constitutions. Wikipedia often provides citizenship information of a subject’s parents.
India requires an application, possibly to not run afoul of the Amendment XIV (complete) jurisdiction requirement. Kamala’s Indian mom doesn’t block her from being an NBC, but her Jamaican dad and the Jamaican constitution do, IMO.
I think only Jews frequently acquire foreign citizenship after being born with American citizenship.
It used to be easy for an Italian-American to get Italian citizenship.
I would think dual citizenship would normally come through a parent via birth and the constitution(s) of the parents’ countries.