keesio said:
If I'm entering Canada on my Canadian passport, I do not write "USA" as my citizenship on my customs declaration card. I put "CANADA" because I am Canadian and CBSA wants me to enter as a Canadian. Likewise when I enter the USA, I enter on my US passport and put down my citizenship as "American". This is expected and confirmed by both CBP and CBSA officials when I was interviewed by both for my NEXUS application. Of cousre if you are asked for more information, you disclose it. No one is arguing that.
You are following the correct course of action. Let nothing I say following this be interpreted otherwise.
The best way to safeguard one's U.S. citizenship after having committed a potentially expatriating act (I have committed several such acts during my lifetime) is to make clear, unambiguous, repeated and well documented statements of one's intent to maintain U.S. citizenship. When I enter Canada, I present myself solely as a Canadian citizen. But, when I fill out a customs form, I ALWAYS include USA in the citizenship box. (It doesn't hurt, and it is one more piece of evidence documenting my intention to maintain U.S. citizenship.)
Before applying for Canadian citizenship and before swearing the oath of citizenship, I swore out statements of my intention to maintain U.S. citizenship and had them notarized. Upon becoming Canadian, I immediately renewed my U.S. passport (even though it was good for several more years) and included a statement that I had naturalized as a Canadian citizen on such-and-such a date, with the intention of maintaining U.S. citizenship. While living outside the U.S., I always vote in U.S. elections for only Democrats or Republicans (no third parties or write ins); I always file tax returns, whether I am required to or not; I always enter the U.S. on a U.S. travel document; and I always go out of my way to write on government forms that I am a U.S. citizen. Even when pulled over by the police in the USA, I present both my Canadian enhanced drivers licence and my US Passport Card. I have established a large body of legal, third party verifiable evidence documenting my intention to maintain U.S. citizenship. I have never committed any act that undermines an intention to maintain U.S. citizenship.
It is my belief that threats to my U.S. citizenship have ceased, in large part, because of my in-your-face, almost belligerent obsession with establishing my unambiguous, clear-cut, straight forward intention to maintain U.S. citizenship. Not only has there never been any legal grounds for threatening my status, I am wealthy enough to fight for my rights and up standing enough to present a positive publicity image in my defence. I have learnt how to gird myself with the armour required to deter capricious attacks to my U.S. status, and I recommend all those who have committed potentially expatriating acts to do likewise.