Originally Posted by Flaflyer

The US seems to be less friendly to the idea of dual citizenship than other parts of the world where it is more common. I see the requirement to only enter/leave on the person’s US passport as an indicator of the government’s attitude that you are either an American or not.

Most dual citizenships seem to arise because of different nationalities of the two parents. A person is dual at birth.

However I can imagine it becomes sticky legally when an adult obtains a new citizenship. I think you need to research this angle carefully. When you obtained you US citizenship, known or unknown to you buried in the fine print, did the forms and procedure require you to renounce all foreign citizenships as part of the process?

If so, the US might consider you renounced your Canadian citizenship. However, unless you tell Canada they may not know. Does Canada allow you to keep your citizenship while swearing an oath to another country? If not, even though you did not contact Canada and renounce your citizenship, technically your Canadian passport may be invalid and using it might get you in trouble.

Worse, if you are questioned at customs anywhere, or get into any issues requiring local police, or lose your passport in China and need to report it, being in a foreign country with a non-valid passport will probably get you on all the worldwide terrorist watch lists forever and you may get hassled by US Customs and get visits to the back room on all your future trips, something no one wants to have happen.

You should check US and Canadian rules and make sure your Canadian passport and citizenship are actually still valid.