How do I prove that I'm not a US citizen?

Could anyone help me with this?
I have lived in the US without a green card and want to return to my home country in Europe.
Since my passport has long expired, the consulate will not issue a travel document for me unless I can show them I have not taken on US citizenship. Since I have lived here illegally, will I run into legal trouble by sending in the the g-639 requesting this information, i.e. ICE agents knocking on my door? Again I want to leave and return to my home country and this would be the only acceptable form of proof that I don't have US citizenship, for the consulate.
I was also told my request under the FOIA could be denied since I am not a US citizen and should instead go to my local ICE or Homeland Security office and request their help in obtaining a passport/travel doc from the consulate and apply for voluntary departure. I want to leave soon and am afraid this prcess could take very long and I could be detained. Don't have a criminal record other than a couple of speeding tickets which I paid. This is a sticky situation for me...
Thanks for any help
did you resolve this issue? were you able to travel?
Did you managed to take care of it. I have the same problems and have nothing but problems.Even if my situation is a little different,but they still want me to provide that i am not a US Citizen.I am lost.If you made it please let me know how . If not,i think we are in a situation where the Sheriffs Department has to make sure we can get back home
hello, how did you resolve this? were you able to travel back?