I have a US passport and a Mexico passport. My US passport has only 1 surname, but my Mexican passport includes my mothers maiden name as a second surname. I want to purchase my US -> Mexico flight ticket using my Mexican passport, since Mexico is my destination. However, will I run into problems with US immigration if my flight information contains both surnames, considering my legal US name only uses one of those surnames?
However, will I run into problems with US immigration if my flight information contains both surnames, considering my legal US name only uses one of those surnames?
No. You might run into trouble with the airline, though.
The US government doesn't much care if your ticket doesn't match your US passport, especially since the ticket matches your other passport. The US government does not inspect departing travelers, in any event. When you return to the US, they will inspect you, of course, whereupon you'll present your US passport and they'll let you in. They cannot deny admission to a US citizen.
When you fly to the US, though, you'll have to show your US passport to check in, and the name won't match the name on the ticket. The airline has two reasons for checking documents on international flights. The first is to verify the identity of the traveler, and the second is to verify that the traveler has the correct documents to enter the destination country. When you fly to Mexico, you'll use your Mexican passport for both purposes. When you return to the US, you'll use your Mexican passport for the first purpose and your US passport for the second.
If anyone questions the name discrepancy, just tell the truth: laws and conventions about names differ. But it's unlikely anyone will ask: surely airlines operating between Mexico and the US encounter this situation frequently, as must US immigration officers.