Ok, here's at least part of my perception. "Dual citizenship" seem to fly in the face of the oath,
I hereby declare, on oath, that I absolutely and entirely renounce and abjure all allegiance and fidelity to any foreign prince, potentate, state, or sovereignty, of whom or which I have heretofore been a subject or citizen; that I will support and defend the Constitution and laws of the United States of America against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I will bear arms on behalf of the United States when required by the law; that I will perform noncombatant service in the Armed Forces of the United States when required by the law; that I will perform work of national importance under civilian direction when required by the law; and that I take this obligation freely, without any mental reservation or purpose of evasion; so help me God.
This makes sense to me. Your oath of citizenship clearly implies that you renounce all others; I wasn’t aware of this.
Here’s the Canadian oath, which is quite different:
“I swear (or affirm) that I will be faithful and bear true allegiance to Her Majesty Queen Elizabeth II, Queen of Canada, her heirs and successors, and that I will faithfully observe the laws of Canada and fulfil my duties as a Canadian citizen.“
Which seems quite compatible with dual citizenship, as long as you obey Canadian laws, fulfil you duties as a Canadian, and bear allegiance to the queen.
Hence my position on dual citizenship.
Were I an American, I might hold a different view, or be campaigning for the oath to be changed, even though it’s quite legal for you to be a dual citizen:
That language seems to firmly establish a principle of “one person, one country.” But even though it sounds unequivocal, it is not. In fact, it is entirely possible for naturalized U.S. citizens to retain citizenship in another country, or for a native-born American to claim citizenship in a second country. On the face of it, this is an odd arrangement that challenges the notion that citizenship is an expression of national loyalty. How can a person be equally loyal to two countries?
Yet dual citizenship has been specifically sanctioned by the United States Supreme Court. In 1967, the court ruled that the State Department had violated the Constitution when it refused to issue a new U.S. passport to a U.S. citizen who had voted in an election in Israel. The decision overturned a law saying that “a person, who is a national of the United States, whether by birth or naturalization, shall lose his nationality by voting in a political election in a foreign state.”
But like you, I’d have a problem taking that vow and feeling good about it if I were also a citizen elsewhere.