I am a UK citizen living in Arizona but I lost my passport. I have a flight from LA to London but need to get to LA and was hoping on getting a flight there, am I able to do this by using a Emergency Travel Document or will I need to find another way on getting to LA. Please help
According to the TSA website, one accepted document is a "foreign government issued passport".
Whether an emergency travel document counts as a passport is up to the officer checking you really; however, if you tell them it's an emergency passport, they're more likely to accept it.
Even if they aren't satisfied, however, you should be able to fly:
In the event you arrive at the airport without valid identification, because it is lost or at home, you may still be allowed to fly. The TSA officer may ask you to complete a form to include your name and current address, and may ask additional questions to confirm your identity. If your identity is confirmed, you will be allowed to enter the screening checkpoint. You may be subject to additional screening.