Originally Posted by Punktlich2
Literally a Canadian-US dual national traveling from Canada to Europe (or elsewhere) would have to use a US and not a Canadian passport.
Not if they aren't passing through the US en route.
Passport data are collected by ICE and other elements of DHS. They are used to conflicts due to dual nationality but many travelers say it avoids issues if they tender the US passport to the airline and present only the EU/EEA/Swiss passport to the immigration police on the European side. US immigration inspectors do not necessarily know such basic things as that dual nationality is perfectly legal for Amcits to have.
Not so sure about this. I've never had anyone question my dual nationality on entry or departure - though you do have to play the game by their rules. Use only the US passport to enter, and it does avoid problems on departure to use the US passport with the airline check-in desk, since what they're actually looking for is the little green "receipt" (i.e. for the VWP) if you show your foreign passport.
I've often shown my French passport when I board the flight home. And I use the French passport on arrival simply because the lines are shorter and move faster.