Actually I feel there is a demand for psychologists equal to Canada or the US in Mexico.There isn't a lot of jobs in psychology in Mexico, but the fact that you studied in the states might give you an edge. It depends on which school you went to and where you apply.
You could always try to go into teaching though.
I was wondering why you think there might not be. My sister in law is a psychiatrist and tells me things about her profession in Mexico sometimes.
There are people in every country with a need that would involve the mental health professions, I would imagine.
Teaching and nursing here are two of the lower paid professions, especially compared to Canada and the US.
My sister in law does very well financially. Excellent in fact.