shorelife, it doesn't work that way today. US citizens born abroad ordinarily retain their US citizenship even in the absence of what you mention unless the US citizen is able and willing to deliberately renounce their US citizenship and actually does deliberately renounce their US citizenship.
US citizens born abroad to US parent(s) -- parent(s) who have filed a report of birth of a US citizen abroad and meet the INA conditions -- do not have US citizenship by way of naturalization but are considered natural-born US citizens as the US has only two categories of US citizens: natural-born US citizens and naturalized US citizens.
Originally Posted by
catocony
There may be a code that requires you to use a US passport, but what is the penalty? Bottom line, they're not going to throw you in jail, and since the US does not do outbound Immigration, there's nothing to catch you there with.
US airlines feed the US government with the passport information of departing passengers, and DHS has been known to use that information to grab (even if just temporarily interrogate/search) passengers on departure from the US. This is not likely to happen in this kind of situation, and the bottom line is this alone is not going to be something any right-thinking US Attorney or USAA is going to waste time pursuing.