Perhaps a deep researching FReeper can/will help us out on that.
I just did a search and found this:(interesting; my last year in LE was 1967)
Dual Citizenship in the United States
Dual citizenship had previously been banned in the United States, but in 1967 the US Supreme Court struck down most laws forbidding dual citizenship.
However, the US government remained disdainful of dual citizenship for some time. To this day, candidates for US citizenship through naturalization are forced to (at least hypothetically) renounce their previous citizenship at the United States naturalization ceremony.
The renouncing of one’s previous citizenship is part of the oath that new US citizens must take, and failing to honor that oath could result in the loss of citizenship in the United States.
Some cases that have been brought before the Department of State in the past involve people who became naturalized US citizens but maintained a residency and life in their country of previous citizenship.
While most countries recognize the Oath of Allegiance in the United States to be a binding contract regarding one’s citizenship, other countries have stated that the oath has no effect on their own citizenship laws. The US government used to aggressively pursue these cases to get the dual citizens to renounce their citizenship, but this is no longer the case.
Additionally, young children who naturalize in the United States along with their parents didn’t take the Oath of Allegiance — even though their parents did — and can technically still hold on to their previous citizenship.
People who have held dual citizenship since birth or childhood — or who became citizens of another country after becoming a US citizen and were not asked to renounce their previous citizenship — can remain dual citizens in the United States.