Please Help Canadian on TN got fired while outside the US

Hi there
I need to know what should I do in this situation. I was working for an american company on a TN Visa. Recently, I got fired while I was in Brazil in a job mission. I got a job at a Brazilian company and I will stay down here in Brazil. However, since I left the US employeed I did not return my I-94. Thus:

What will happen when I try to reenter the US?
Should I return the I 94 at a local US Consulate?

I dont wanna do anything illegal that my cause me problems in the future.

Please help solve this problem.

Thanks a lot !!!

I would simply return the I-94 to the consulate.