SCOTUS ruled in the cases I cited to you that the US recognizes dual citizenship. It is the law of the land and has been for more than 30 years. The State Department implements and enforces the laws, not make them.
I know very well about people claiming dual citizenship, having assisted friends and family having members of their families who had to deal with dual citizenship problems.
I have firsthand knowledge of the issue professionally and personally. I have issued passports. My wife is an immigrant and naturalized citizen and my daughter was born overseas.
I obtained the information directly from the Department of State website which carefully described the difference between the court cases restraining enforcement of laws against dual citizenship, while warning readers and candidates for dual citizenship that the U.S. Government did not recognize dual citizenship. Evidently, you are joining with the Obama Administration in trying to consign the former disapproval of dual citizenship to the memory hole and pretend it did not exist when in fact it did exist not so long ago.
The US did not always recognize dual citizenship. I provided you with the legal cases that changed the laws on dual citizenship. Facts are stubborn things. What started this exchange was your statement that the US does not recognize dual citizenship. It does and has been doing so for decades.
I don't agree with the concept of dual citizenship, but it is the law of the land. Much of it stems from Israel's law of return that makes any Jew eligible to be a citizen of the state of Israel--a result of the Holocaust and the establishment of the country. Once you allow Jews to hold dual citizenship, it is very difficult to deny it to others from different countries. And SCOTUS affirmed that it is constitutional. It may take a constitutional amendment to change it.
It is a given that the Democrats are moving Heaven and Earth in Congress, the Federal judiciary, and the executive administrations to change and/or eliminate the very concept of nationhood and citizenship. There are even some members of the Obama Administration and previous administrations who are publicly proposing a North American Union in preparation for the fantasy of a One World Government. Removing the distinction of citizenship and allegiance to a nation are necessary steps towards achieving such goals. That does not mean U.S. Citizens must agree to surrendering their present sovereignty over the personal and public affairs by delegating and ceding them to these international super-governments and their spectacularly corrupt bureaucrats. If push comes to shove, the Democrats and their socialist-communist members may provoke a response in the form of new Constitutional amendments or a Constitutional Convention which even the most corrupt members of the Congress, Supreme Court, and Executive administration will find difficult to ignore and subvert without being impeached and/or prosecuted, no matter what political party they profess to represent.
As for the legality of dual citizenship, there is a huge difference between statutory law and the decisions of SCOTUS interpreting or misinterpreting the Constitution, international law, and natural law. The Obama Administration may ultimately succeed in provoking a response which will settle the dual citizenship and a variety of immigrations issues contrary to their intended goals.