As a dual national, can I leave the US with my other passport since?
Legally? No. US law requires US citizens to enter and depart the US using their US passport. However, the US has no positive exit controls, so boarding an outbound flight is usually no issue unless the CBP does a spot inspection of outbound passengers. This does happen from time to time, often when CBP is looking for a wanted outbound passenger on the flight. Returning to the US, however, is going to be impossible without a US passport unless one is also a Canadian citizen. All other nationals require a valid ESTA or US visa, both of which cannot be issued to a US citizen. You would have to make arrangements to have your US passport couriered to your location when it is received at the address you gave the Department of State. If there is any delay for any reason that requires your presence to address, youre in a pickle. Youre stuck unless youre willing to gamble.