What is dual citizenship and what is the U.S. governments stance on it?

Dual nationality involves possessing citizenship from two countries at once.  It may be It used to be that dual citizenship was prohibited in the U.S., but the 1967 case of Afroyim v. Rusk and the 1980 ruling in Vance v. Terrazas struck down the majority of the laws making it illegal to hold such a citizenship status.  Today, while the State Department does not favor dual citizenship, rules prohibiting the latter in the U.S. are only applicable in theory to individuals seeking to become naturalized.  One of the reasons that the United Sates government does not encourage citizenship american as well as that of another country is that it feels that it may hinder its ability to help citizens overseas.