Originally Posted by
megaloman
As US citizen, you have to leave the US using your US passport, so that passport details have to be on your boarding pass.
No. You have to "bear" a US passport. No requirements to have the data on your PNR.
The US government does not care about a US citizen having mismatched entry/exit records.
The US government does not have the capacity to detain an apparent foreigner leaving the US but having no entry records.