score:3
Leaving the US would indeed likely be no issue. However you are not going to be able to board the flight to US using your Philippine passport, unless you have a valid US visa in it (for which you're not eligible as US citizen). The airline will ignore your claim of US citizenship - they have no means to verify it - and will refuse you to board the flight.
So once you leave, you have two option for returning into US:
Obtain a new US passport in the US Embassy in Manila;
Obtain the Canadian or Mexican visa in your Philippine passport, and enter the US overland from those countries.