I'm an American citizen. I was born in the US, however I came to visit Ecuador on an emergency basis using my Peruvian passport. I lost my US passport and had no time to get one before coming to Ecuador. Can I fly back to the US with my Peruvian passport only or will I be denied entry? I have my US drivers license, and SS card on me. I don't have a visa since I am a citizen and resident in the US.
A US citizen cannot be denied entry to the USA, although you can expect to be held at the border for sometime while your citizenship is verified.
None of that will matter, because no airline will allow you to board a flight to the US with only a Peruvian passport if you don't have a visa.
You should go to the US embassy in Quito who will be able to issue an emergency travel document that will allow you to get home.